Author: DIYMeter Team

A 12 × 12 ft room has 144 sq ft of floor, but you should order a piece 12 ft wide by about 12 ft 6 in long, which is 150 sq ft or about 16.7 square yards. The extra few inches at each end let the fitter trim the carpet tight to the walls.

Carpet is cut from a roll of fixed width, so the amount you pay for depends on how the room fits that roll, not only on its area. Here is how to work it out for any room.

Quick answer: carpet by room size (12 ft roll)

These sizes assume a standard 12 ft wide roll, which is the most common width in the US and Canada, with 3 inches of trim allowance at each end.

Room size	Floor area	Cut size to order	Carpet to buy
10 × 10 ft	100 sq ft	12 × 10 ft 6 in	126 sq ft (14.0 sq yd)
10 × 12 ft	120 sq ft	12 × 10 ft 6 in	126 sq ft (14.0 sq yd)
11 × 13 ft	143 sq ft	12 × 13 ft 6 in	162 sq ft (18.0 sq yd)
12 × 12 ft	144 sq ft	12 × 12 ft 6 in	150 sq ft (16.7 sq yd)
12 × 14 ft	168 sq ft	12 × 14 ft 6 in	174 sq ft (19.3 sq yd)
12 × 15 ft	180 sq ft	12 × 15 ft 6 in	186 sq ft (20.7 sq yd)

Notice that a 10 × 10 room costs the same as a 10 × 12 room. You still have to buy the full 12 ft width, and the extra 2 ft is cut off and wasted.

How to work it out

1. Measure the room at its widest and longest points. Go into door openings and bay windows. Measure to the nearest inch, or to the nearest centimetre.
2. Turn the room to fit the roll. If one side is 12 ft or less, run the roll’s 12 ft width across that side. Your cut length is the other side.
3. Add trim. Add 3 inches (about 7.5 cm) at each end of the length. Add the same to the width if the room is almost exactly as wide as the roll.
4. Multiply. Roll width × cut length = what you pay for. Divide square feet by 9 to get square yards.

If the room is wider than the roll in both directions, you will need a seam. Plan where it goes before you buy. Keep seams out of doorways and main walkways, and make sure both pieces have the pile running the same way, otherwise they will look like two different colours. This is when a 15 ft roll, or a fitter’s measure, earns its keep.

The DIYMeter carpet calculator handles the roll width and trim for you, in feet or metres.

Roll widths in the UK, Australia and Canada

• UK: carpet is mostly sold from 4 m and 5 m wide rolls and priced per m². A 3.5 × 4 m bedroom fits a 4 m roll, so you would order 4 m × 3.6 m, which is 14.4 m² for a 14 m² room.
• Australia: common widths are 3.66 m (12 ft) and 4 m, priced per metre or per m².
• Canada: mostly 12 ft rolls, priced per square foot or square yard, the same as the US.

Underlay and gripper

• Underlay (carpet pad). Underlay comes in narrower rolls and is laid in strips, so you only need the floor area plus about 5%. A 12 × 12 room needs about 151 sq ft (14 m²).
• Gripper or tack strip. This goes round the edge of the room but not across doorways. A 12 × 12 room has a perimeter of 48 ft. Take off about 3 ft for the door and you need 45 ft. It is usually sold in 4 ft (1.2 m) lengths, so that is 12 lengths.
• Door bars and thresholds. You need one for each doorway where the carpet meets another floor.

Stairs

Measure each stair as the depth of the tread, plus the height of the riser, plus about 2 inches (5 cm) to wrap over the nosing. Multiply by the number of stairs. A typical straight flight of 13 stairs, with each one taking about 21 inches of carpet, needs about 23 ft of length cut from a 3 ft wide runner, or one strip from the main roll. The stair calculator can help you check the riser and tread sizes.

Common mistakes

• Buying the floor area only. The roll width decides what you pay for. Always work out the cut size.
• Forgetting the pile direction. Pile should run towards the main door or the window, and every piece in a room must run the same way.
• Ignoring patterns. Patterned and striped carpets need extra length, often one full pattern repeat, so the seams line up.

FAQs

How many square yards is a 12 × 12 room? The floor is 16 sq yd. With trim allowance you will buy about 16.7 sq yd.

Is it cheaper to buy a remnant? Often yes. Remnants are offcuts at the end of a roll, and a 12 × 13 ft piece can be a fraction of the full price, so it is worth asking.

Can I lay carpet myself? Underlay and gripper are an easy DIY job. Stretching the carpet properly needs a power stretcher and a knee kicker, which most people hire or leave to a fitter.

Related: the DIY Project Budget & Materials Planner turns your measurements into quantities, costs and a shopping list.

Most asphalt shingles are packed three bundles to a “square”, and one square covers 100 sq ft of roof. So a roof with 2,000 sq ft of plan area (the footprint including the overhangs) at a common 6/12 pitch needs about 74 bundles once you add 10% for waste.

The catch is that the roof surface is always bigger than the footprint, because it slopes. Below is how to allow for that, a quick table, and the extras people forget to order.

Quick answer: bundles by roof size

These figures assume a 6/12 pitch, a simple gable roof, 10% waste and three bundles per square.

Roof plan area (incl. overhangs)	Actual roof area	Squares (with waste)	Bundles
1,000 sq ft	1,118 sq ft	12.3	37
1,500 sq ft	1,677 sq ft	18.4	56
2,000 sq ft	2,236 sq ft	24.6	74
2,500 sq ft	2,795 sq ft	30.7	93

For a hip roof, or a roof with valleys and dormers, use 15% waste instead of 10%. That adds three or four bundles on a 2,000 sq ft roof.

How to work it out

1. Measure the plan area. Measure the length and width of the house and add the eave and gable overhangs. A 50 × 36 ft house with 1 ft overhangs all round is 52 × 38 = 1,976 sq ft of plan area.
2. Find the pitch. Pitch is how many inches the roof rises for every 12 inches it runs. Put a level on the rafter or roof, measure 12 inches along it, then measure straight up to the roof. A 6 inch rise means 6/12.
3. Multiply by the pitch factor from the table below to get the real sloped area.
4. Add waste. Add 10% for a plain gable roof and 15% for hips, valleys and lots of cuts.
5. Convert to squares and bundles. Divide by 100 for squares, then multiply by three for bundles. Always round up.

Pitch factors

Pitch	Multiply plan area by
4/12	1.054
5/12	1.083
6/12	1.118
7/12	1.158
8/12	1.202
9/12	1.250
10/12	1.302
12/12	1.414

Worked example. A 1,976 sq ft plan area at 8/12 pitch is 1,976 × 1.202 = 2,375 sq ft of roof. A hip roof needs 15% waste, which makes it 2,731 sq ft, or 27.3 squares. At three bundles per square that is 81.9, so order 82 bundles.

If you would rather skip the arithmetic, the DIYMeter roofing calculator does all five steps for you, in feet or metres.

Check the bundle label first

Three bundles per square is the norm for standard 3-tab and most architectural (laminated) shingles. Some heavier designer shingles come four or even five bundles to a square. The coverage is printed on every bundle, so check it before you order.

Don’t forget the extras

• Starter strip. You need this along every eave and rake edge. Measure those edges and buy starter shingles by the linear foot shown on the pack.
• Ridge and hip cap. Add up the length of all the ridges and hips. One bundle of cap shingles usually covers 20 to 35 linear feet, depending on the brand.
• Underlayment. Many synthetic underlayment rolls cover about 10 squares, and a roll of #15 felt covers roughly 4 squares. Check the label, because roll sizes vary.
• Drip edge. Comes in 10 ft lengths. Divide the total eave and rake length by 10 and round up.
• Nails. With four nails per shingle you need about 2 to 2.5 lb of roofing nails per square. In high-wind areas, where codes ask for six nails, allow about half as much again.
• Ice and water shield. Most building codes in cold regions of the US and Canada require it along the eaves, and it is wise in valleys anywhere.

Working in metres?

One square is 100 sq ft, which is about 9.29 m². To convert, divide your roof area in m² by 9.29 to get squares. A roof of 230 m² is about 24.8 squares before waste.

Asphalt shingles are common in the US, Canada and parts of Australia. In the UK most pitched roofs are tiled or slated, and those are counted per m² from the gauge and the tile size rather than in squares.

Common mistakes

• Using the floor area of the house. The roof is larger because of the overhangs and the slope. On a steep roof the difference can be 30% or more.
• Forgetting garages and porches. Measure every roof plane that is being re-roofed.
• Ordering exactly the number you calculated. Shingles come from dye lots, and a bundle bought later may not match in colour. One or two spare bundles are cheap insurance, and most suppliers will take back unopened bundles.

FAQs

How many square feet does a bundle of shingles cover? About 33.3 sq ft when there are three bundles to a square.

Can I walk on a 9/12 roof? Anything steeper than about 7/12 is hard to walk on safely. Use roof jacks and a harness, or leave it to a roofer.

Related: the DIY Project Budget & Materials Planner turns your measurements into quantities, costs and a shopping list.

A 12 × 12 ft room with 8 ft ceilings needs about 17 sheets of 4 × 8 ft drywall to cover the walls and the ceiling, allowing for one door, a window and 10% waste. If you are only hanging the walls, it is about 12 sheets. With larger 4 × 12 ft sheets, the whole room takes about 12.

Below is exactly how that is worked out, a table for other common room sizes, and the screws, tape and joint compound you will need to go with it. For your own measurements, the drywall calculator does it in seconds.

Quick answer: drywall sheets by room size

All figures assume 8 ft walls, about 36 sq ft of doors and windows taken off, and 10% extra for cuts and mistakes.

Room size	Area (walls + ceiling)	4 × 8 sheets, walls + ceiling	4 × 8 sheets, walls only	4 × 12 sheets, walls + ceiling
10 × 10 ft	384 sq ft	14	10	9
10 × 12 ft	436 sq ft	15	11	10
12 × 12 ft	492 sq ft	17	12	12
12 × 14 ft	548 sq ft	19	14	13
14 × 16 ft	668 sq ft	23	16	16

With 9 ft walls, add one or two sheets: a 12 × 12 room with 9 ft walls and a ceiling needs about 19 sheets of 4 × 8.

How to work it out

1. Wall area. Add the lengths of all four walls and multiply by the height: (12 + 12 + 12 + 12) × 8 = 384 sq ft.
2. Take off openings. A standard interior door is about 21 sq ft and an average window about 15 sq ft. One of each is 36 sq ft, leaving 348 sq ft of wall.
3. Add the ceiling. 12 × 12 = 144 sq ft, for a total of 492 sq ft.
4. Add waste. 492 × 1.10 = 541 sq ft.
5. Divide by the sheet size and round up. A 4 × 8 sheet covers 32 sq ft, so 541 ÷ 32 = 16.9. Buy 17 sheets.

Many experienced hangers do not subtract openings at all, because the offcuts from around doors and windows rarely get reused. If you work that way, the same 12 × 12 room comes to 19 sheets. Either approach works; the second just leaves you more spare.

4 × 8 or 4 × 12 sheets?

Longer sheets mean fewer joints, and joints are where most of the finishing time goes. On an 8 ft wall, 4 × 12 sheets hung horizontally leave fewer butt joints and a flatter wall. The catch is weight and handling: a 1/2 inch 4 × 12 sheet weighs around 70–80 lb, which is a two-person lift, and it will not fit in most cars or through tight stairwells.

• Choose 4 × 8 if you are working alone, carrying sheets up stairs or hanging small, broken-up walls.
• Choose 4 × 12 for long, open walls and ceilings when you have help and delivery.

Which thickness?

• 1/2 inch is standard for interior walls in most homes.
• 1/2 inch sag-resistant or 5/8 inch is often used on ceilings, especially with joists at 24 inch centres, because standard board can sag over time.
• Moisture-resistant board is a common choice for bathrooms and laundry rooms. Behind tiles in a shower, a cement board or a dedicated tile-backer is normally required.
• Fire-rated (Type X) board is usually required by code in some locations, such as walls between an attached garage and the house. Check your local code.

Screws, tape and joint compound

For the 17-sheet room:

• Screws: about 32 per 4 × 8 sheet, so around 550. Use 1-1/4 inch coarse-thread screws for wood studs. They are sold by weight, so check the count on the box and buy enough for about 550, plus a few spare.
• Joint tape: a single 500 ft roll of paper tape is plenty for a room this size. Add inside-corner tape or metal corner bead for the outside corners.
• Joint compound: as a rough guide, one 4.5 gallon bucket of all-purpose ready-mixed compound finishes around 400–500 sq ft of board with three coats. Buy one bucket plus a smaller one, or two if the room has lots of corners.

At typical US prices in September 2026, a 1/2 inch 4 × 8 sheet costs around $16, so 17 sheets are about $272 before screws, tape and compound.

If you measure in metres: plasterboard

In the UK and Australia, the same material is called plasterboard and is usually sold in 1.2 × 2.4 m sheets (2.88 m² each). A 3.6 × 3.6 m room with 2.4 m walls, 3.3 m² of openings and a ceiling has about 44 m² to cover. With 10% waste that is 48.6 m², or 17 sheets. Switch the drywall calculator to UK or Australia to work in metres.

Common mistakes

• Forgetting the ceiling. It is a full extra room’s worth of floor area, and ceiling sheets are the hardest to hang, so it is worth planning them first.
• No spare for damage. Corners crush easily in transit. Ten per cent waste covers normal cuts and the odd damaged sheet.
• Joints in line with door corners. A joint that runs straight off the corner of a door or window is likely to crack. Plan sheets so the board wraps around the corner and the joint falls in the middle of the opening.
• Not checking stud spacing. Sheet edges must land on a stud or joist. Measure your framing before you order longer sheets.

Frequently asked questions

How many sheets of drywall for a 12×12 room without the ceiling?

About 12 sheets of 4 × 8, or 8 sheets of 4 × 12, allowing for one door, one window and 10% waste.

How many sheets of drywall for a 10×10 room?

About 14 sheets of 4 × 8 for the walls and ceiling, or 10 sheets for the walls only.

Should I hang drywall vertically or horizontally?

On walls up to about 8 ft, many pros hang sheets horizontally because it creates fewer seams and a stronger wall. Vertical hanging can be easier for one person and is common on taller walls. Ceilings always go first.

How much does it cost to drywall a 12×12 room?

For materials only, expect around $270 for 17 standard sheets, plus roughly $50–$80 for screws, tape and compound at typical 2026 prices. Professional hanging and finishing labour is extra and varies widely by area.

Work out your own room: the free drywall calculator gives sheets, screws and tape for any room in feet or metres. Painting afterwards? The paint calculator covers that, and remember new drywall needs a coat of primer first.

Figures are estimates for planning. Sheet sizes, prices and local building codes vary, so check with your supplier and local building department before you buy.

Related: the DIY Project Budget & Materials Planner turns your measurements into quantities, costs and a shopping list.

Most emulsion paints cover about 10–13 m² per litre for each coat on smooth, already-painted walls. For an average bedroom of 3.6 × 3.6 m with 2.4 m ceilings, that means roughly 5.4 litres for two coats on the walls, so three 2.5 litre tins, or a 5 litre tin plus a 1 litre tin.

This guide shows how to measure a room, how to turn square metres into litres, how much extra to allow for new plaster and colour changes, and a quick table for common room sizes. If you would rather skip the sums, the paint calculator does it for any room.

Quick guide: paint for common room sizes

These figures assume 2.4 m high walls, one door, two windows, two coats and a coverage of 11 m² per litre, which is typical for a standard matt or silk emulsion. Ceilings are listed separately because they are often painted in a different colour or product.

Room (floor size)	Wall area to paint	Walls, 2 coats	Ceiling, 2 coats
Small bedroom (3 × 3 m)	24 m²	4.4 litres	1.6 litres
Average bedroom (3.6 × 3.6 m)	30 m²	5.4 litres	2.4 litres
Double bedroom (4 × 3.5 m)	31 m²	5.7 litres	2.5 litres
Living room (4.5 × 4 m)	36 m²	6.6 litres	3.3 litres
Large living room (5 × 4 m)	38.5 m²	7.0 litres	3.6 litres

Always check the coverage printed on your tin. Cheaper paints often cover less, and some one-coat or high-opacity products claim more.

Step 1: measure the walls

You only need three measurements: the length and width of the room, and the height from the floor to the ceiling.

1. Add up the length of all four walls. For a 3.6 × 3.6 m room that is 3.6 + 3.6 + 3.6 + 3.6 = 14.4 m. For a rectangular room, it is 2 × (length + width).
2. Multiply by the wall height. 14.4 × 2.4 = 34.6 m² of wall.
3. Take off doors and windows. A standard internal door is about 1.9 m² and an average window about 1.4 m². With one door and two windows, that is 34.6 − 1.9 − 2.8 = 29.9 m² to paint.

If your windows are very large, such as patio doors or a bay, measure them properly and subtract the real area. For small windows, many decorators do not bother subtracting them, which gives a little built-in spare.

Step 2: turn square metres into litres

The formula is simple:

Litres = wall area × number of coats ÷ coverage per litre

For the example room: 29.9 m² × 2 coats ÷ 11 m² per litre = 5.4 litres.

Paint is sold in fixed tin sizes, so the last step is choosing tins. In the UK, emulsion usually comes in 1, 2.5, 5 and 10 litre tins. For 5.4 litres you could buy three 2.5 litre tins (7.5 litres) or one 5 litre tin and one 1 litre tin (6 litres). The second option leaves less waste and is often cheaper per litre. In Australia, 4 litre and 10 litre cans are more common, so a single 4 litre can plus a 2 litre can would do the same room.

Do you really need two coats?

Almost always, yes. One coat can look fine when it is wet, but it usually dries patchy, especially on the edges you cut in with a brush. Two coats give an even colour and a finish that lasts. Plan for more in these situations:

• Big colour changes. Going from a dark colour to a light one, or light to a strong red or yellow, often needs a third coat. A tinted primer or undercoat can save a coat of your more expensive top coat.
• New plaster. Fresh plaster is thirsty and soaks paint in. Seal it first with a mist coat: a first coat of matt emulsion thinned with water, following the tin or plaster manufacturer’s guidance. Allow roughly an extra coat’s worth of paint for it.
• Rough or textured walls. Artex, bare brick and heavily textured surfaces can use 20–30% more paint than smooth walls because there is simply more surface.

Ceilings, woodwork and extras

Measure the ceiling as length × width. The 3.6 × 3.6 m bedroom has a 13 m² ceiling, so two coats at 11 m² per litre need about 2.4 litres: one 2.5 litre tin of ceiling or matt white.

Skirting boards, door frames and windows need a separate trim paint such as satinwood or gloss. These go much further, because the surface area is small: a 750 ml tin usually does the woodwork in an average room, with two coats.

Do not forget the kit. For a typical room you will need a roller and tray, a 2 inch brush for cutting in, masking tape, dust sheets, filler and sandpaper for repairs, and a sugar soap solution to clean the walls first.

If you measure in feet and gallons

In the US, a gallon of interior paint typically covers 350–400 sq ft per coat. A 12 × 12 ft room with 8 ft walls has 384 sq ft of wall; minus one door (about 21 sq ft) and two windows (about 15 sq ft each) that leaves 333 sq ft. Two coats at 350 sq ft per gallon need 1.9 gallons, so two 1-gallon cans. Switch the paint calculator to USA to work in feet and gallons.

Tips to avoid running short (or wasting a tin)

• Buy everything at once. Colours can vary slightly between batches. If you need more than one tin, pour them into a larger bucket and mix them together, a trick called boxing.
• Keep a little back. A small amount of leftover paint is handy for touch-ups. Label the tin with the room and date.
• Check the coverage, not just the price. A cheaper paint that needs three coats can cost more than a better one that covers in two.
• Write down your measurements. It makes it easy to recalculate if you change colour or product in the shop.

Frequently asked questions

How many square metres does 1 litre of paint cover?

Usually 10–13 m² per coat on a smooth, previously painted wall. That drops on new plaster or rough surfaces. For two coats, 1 litre covers roughly 5–6 m² of wall.

Is 5 litres of paint enough for a bedroom?

For an average bedroom of around 3.6 × 3.6 m, 5 litres is just short for two coats on the walls, which need about 5.4 litres. A small bedroom of 3 × 3 m needs about 4.4 litres, so 5 litres is enough.

How much paint do I need for a ceiling?

Multiply the ceiling length by the width, double it for two coats and divide by the coverage. A 4 × 3.5 m ceiling is 14 m², so about 2.5 litres for two coats.

Does darker paint need more coats?

Strong, dark colours often need three coats for an even finish, especially over a lighter base. Some manufacturers recommend a coloured base coat first. Check the tin.

Work out your own room: the free paint calculator takes off doors and windows and tells you how many tins to buy. Papering one wall instead? Try the wallpaper calculator.

Figures are estimates for planning. Coverage varies by product and surface, so check the tin before you buy.

Related: the DIY Project Budget & Materials Planner turns your measurements into quantities, costs and a shopping list.

The quick answer: a 10×10 ft patio is 100 sq ft (9.29 m²). With standard 4×8 in brick pavers you need 450 pavers, or about 495 pavers once you add 10% for cuts and breakage. Larger 12×12 in slabs need just 110 including waste.

The exact number depends on the paver size and the laying pattern. If your patio is a different size or shape, the free paver calculator does the maths for you, including waste.

Pavers for a 10×10 patio at a glance

Paver size	Per sq ft	Per m²	10×10 patio (no waste)	With 10% waste
4 x 8 in (approx. 100 x 200 mm)	4.5	48.4	450	495
6 x 6 in (approx. 150 x 150 mm)	4	43.1	400	440
6 x 9 in (approx. 150 x 225 mm)	2.67	28.7	267	294
12 x 12 in (approx. 300 x 300 mm)	1	10.8	100	110
16 x 16 in (approx. 400 x 400 mm)	0.56	6.05	57	62
24 x 24 in (approx. 600 x 600 mm)	0.25	2.69	25	28

Metric sizes are approximate equivalents. If you buy true metric pavers, work from their actual size: for example, 100 x 200 mm pavers are exactly 50 per m², so a 9.29 m² patio needs 465 before waste.

How to work it out

1. Measure the patio area: length x width. 10 ft x 10 ft = 100 sq ft (3.05 m x 3.05 m = 9.29 m²).
2. Work out the area of one paver in the same units. A 4×8 in paver is 32 sq in, and 32 ÷ 144 = 0.222 sq ft.
3. Divide the patio area by the paver area: 100 ÷ 0.222 = 450 pavers.
4. Add waste: 10% for straight patterns such as running bond or stack bond, 15% for herringbone, diagonal layouts or curved edges.
5. Round up to a whole paver, then up again to whole pallets or packs if that is how they are sold.

Worked example: 10×10 herringbone patio

You want a 10×10 ft patio in classic 4×8 in pavers laid in a 45° herringbone pattern. The area is 100 sq ft, so the base count is 100 x 4.5 = 450 pavers. Herringbone needs more cuts along every edge, so use 15% waste: 450 x 1.15 = 517.5, which rounds up to 518 pavers.

Many suppliers sell pavers by the square foot or by the pallet rather than one by one. In that case order 115 sq ft of coverage (about 10.7 m²) and keep any leftovers for future repairs, since colours can vary between production batches.

Base, sand and edging for a 10×10 patio

Pavers are only as good as what sits underneath them. For a patio with foot traffic, a typical build-up is:

• Gravel base, 4 in (100 mm) compacted: 100 sq ft x 0.333 ft = 33.3 cu ft, or about 1.23 cubic yards (0.93 m³). Crushed stone weighs roughly 1.4 tons per cubic yard, so that is about 1.7 US tons (1.6 tonnes). Add 10–15% because the stone compacts, so order around 1.4 cubic yards.
• Bedding sand, 1 in (25 mm): 100 x 0.083 ft = 8.33 cu ft, or about 0.31 cubic yards (0.23 m³). At a typical 0.5 cu ft per 50 lb bag, that is 17 bags.
• Edge restraint: the perimeter is 40 ft (12.2 m). Subtract any side that runs against the house or an existing wall.
• Jointing sand: a 10×10 patio often takes one to three bags of polymeric sand, depending on joint width and paver shape. Check the coverage on the bag.

Driveways need a deeper base, often 8–12 in (200–300 mm). Use the gravel calculator to size the base for any depth.

Common mistakes

• Forgetting waste. Ordering exactly 450 pavers almost always leaves you a few short after cutting the edges.
• Mixing up nominal and actual sizes. A paver sold as 4×8 may be slightly smaller to allow for joints. Small differences add up over 100 sq ft, so use the size on the spec sheet.
• Skipping the base. Laying pavers straight on soil leads to sinking and weeds within a season or two.
• Buying from different batches. Order everything at once so the colour matches across the whole patio.
• Ignoring slope. Build in a fall of about 1/8 in per foot (around 1%) away from the house so water drains off.

Frequently asked questions

How many pavers are on a pallet?

It varies widely by size and manufacturer. A pallet of 4×8 in pavers often covers roughly 100–150 sq ft, so a 10×10 patio may need one pallet, but check the coverage your supplier lists before ordering.

How much does waste really add?

For a simple square patio in running bond, 5–10% is usually enough. Herringbone, diagonal layouts, curves or lots of corners can push it to 15%.

How many 12×12 pavers for a 10×10 patio?

A 12×12 in paver covers exactly 1 sq ft, so you need 100 pavers, or 110 with 10% waste.

Do I need to account for the joints?

Joints are usually only 1/16–1/8 in (2–3 mm) wide, so they barely change the count. Most installers ignore them and let the waste allowance cover the difference.

Related: the DIY Project Budget & Materials Planner turns your measurements into quantities, costs and a shopping list.

The quick answer: a straight 100 ft fence with posts 8 ft apart needs 14 posts. With posts 6 ft apart, you need 18 posts. Add one extra post for each gate and each change of direction that is not already counted.

This guide explains the formula, gives post counts for other fence lengths, and shows how much concrete, rails and boards to order. For your exact layout, use the fence calculator, which handles feet, metres and panel fences.

The fence post formula

Posts = (fence length ÷ post spacing), rounded up, + 1

For 100 ft at 8 ft spacing: 100 ÷ 8 = 12.5, which rounds up to 13 sections. Add one for the post at the far end, giving 14 posts. The extra one is needed because every section has a post at each end, and the sections share the posts between them.

Fence posts for other lengths

Fence length	Posts at 6 ft spacing	Posts at 8 ft spacing
25 ft	6	5
50 ft	10	8
75 ft	14	11
100 ft	18	14
150 ft	26	20
200 ft	35	26

These counts are for a single straight run. For a fence around three sides of a garden, add up the total length, work out the posts, then add one post for each corner. Each gate needs its own post on both sides, and gate posts should be heavier, such as 6 × 6 in instead of 4 × 4 in.

Metric and panel fences

In the UK, panels are usually 6 ft (1.83 m) wide. With a 100 mm post between each panel, each bay takes up about 1.93 m. For a 30 m run:

• Panels: 30 ÷ 1.93 = 15.5, so 16 panels (one cut down to fit)
• Posts: 16 + 1 = 17 posts

How much concrete per post?

A common setup is a 4 × 4 post in a hole 10 inches wide and about 30 inches deep. After taking away the space the post takes up, the hole holds about 1.15 cubic feet of concrete.

• 80 lb bags (about 0.6 cu ft each): 2 bags per post, so 28 bags for 14 posts.
• 50 lb fast-setting bags (about 0.375 cu ft each): 3 bags per post, so 42 bags.
• UK 20 kg postmix bags: typically 1–2 bags per post, depending on hole size.

As a rule of thumb, bury about one third of the post. A 6 ft high fence needs posts around 8–9 ft long, set about 2–3 ft into the ground. In areas where the ground freezes, the hole should go below the frost line.

Rails and fence boards

For a 100 ft wooden privacy fence with 8 ft sections:

• Rails: 2 rails per section for fences up to 4 ft high, 3 rails for a 6 ft fence. That is 13 × 3 = 39 rails of 8 ft.
• Boards (pickets): with 5.5 in boards fitted tight, each 8 ft section needs about 18 boards, so around 234 boards. Add 5–10% for splits and warped boards.
• Fixings: two nails or screws per board on each rail, so six per board on a 3-rail fence.

Common mistakes

• Forgetting the “+ 1” and ending up one post short.
• Not adding posts for gates, or using light posts to hang a gate.
• Measuring along a curved or sloped line and assuming it is straight.
• Setting posts too shallow, which lets the fence lean in strong wind.

Frequently asked questions

What is the best spacing for fence posts?

Most wooden fences use 6 to 8 ft spacing. Use 6 ft on windy or exposed sites or for heavy boards. Chain-link fences often use up to 10 ft, and panel fences follow the panel width.

How many fence posts for 200 feet?

26 posts at 8 ft spacing, or 35 posts at 6 ft spacing, for a straight run.

Do corner posts count as extra posts?

A corner post ends one straight run and starts the next. If you work out each side separately, count the corner post only once, not twice.

Can I use gravel instead of concrete?

Yes. Tightly packed crushed stone drains well and can make posts last longer, but concrete is stronger in soft soil and for gate posts.

Related: the DIY Project Budget & Materials Planner turns your measurements into quantities, costs and a shopping list.

The quick answer: for a new lawn, lay 4 to 6 inches (100–150 mm) of topsoil. At 4 inches, you need about 12.3 cubic yards for every 1,000 sq ft. In metric, 1 m³ covers 10 m² at 100 mm deep. Add around 10% because topsoil settles.

This guide covers the formula, a coverage table for common depths, and how many bags you would need for smaller jobs. For an instant figure in cubic yards, m³, tonnes or bags, use the topsoil calculator.

Topsoil coverage at a glance

Depth	1 cubic yard covers	Depth	1 m³ covers
1 in	324 sq ft	25 mm	40 m²
2 in	162 sq ft	50 mm	20 m²
4 in	81 sq ft	100 mm	10 m²
6 in	54 sq ft	150 mm	6.7 m²

How to work it out

1. Measure the area in square feet or square metres. Split odd shapes into rectangles and add them up.
2. Multiply by the depth. Convert inches to feet (÷ 12) or millimetres to metres (÷ 1,000) first.
3. Convert cubic feet to cubic yards by dividing by 27.
4. Add 10–15% for settling and uneven ground.

Worked examples

US lawn: 1,000 sq ft at 4 inches deep.

• Volume: 1,000 × (4 ÷ 12) = 333 cubic feet
• Cubic yards: 333 ÷ 27 = 12.3 yd³
• With 10% extra: about 13.5 cubic yards

UK lawn: 50 m² at 100 mm deep.

• Volume: 50 × 0.1 = 5 m³
• With 10% extra: 5.5 m³
• Weight: at about 1.3 tonnes per m³, that is roughly 7 tonnes

How deep should topsoil be?

Job	Recommended depth
Top dressing an existing lawn	1/4–1/2 in (6–12 mm)
Levelling low spots	1–2 in (25–50 mm) at a time
New lawn from seed or turf	4–6 in (100–150 mm)
Flower beds and borders	6–8 in (150–200 mm)
Vegetable beds and raised beds	8–12 in (200–300 mm)

Grass roots do most of their work in the top few inches, but a deeper layer of good soil holds water better and helps the lawn survive dry spells.

How much does topsoil weigh?

Dry topsoil weighs roughly 1 to 1.1 tons per cubic yard, or about 1.2–1.4 tonnes per m³. Wet soil can weigh much more. This matters if you are collecting it in a trailer or ordering by weight: a small trailer or pickup can often carry less than one cubic yard safely.

Bags or bulk?

Bagged topsoil is handy for small jobs but gets expensive quickly.

• A 1 cu ft bag: 27 bags make one cubic yard.
• A 0.75 cu ft bag: 36 bags make one cubic yard.
• A 25 litre bag: 40 bags make one m³.
• A bulk bag in the UK is usually close to 1 m³, or about 0.8–1 tonne.

For anything over about one cubic yard or one cubic metre, bulk delivery is usually far cheaper per unit than bags.

Raised beds

For a 4 × 8 ft raised bed 12 inches deep, the volume is 4 × 8 × 1 = 32 cubic feet, or about 1.2 cubic yards. A 1.2 × 2.4 m bed 300 mm deep holds 0.86 m³. Many gardeners fill raised beds with a mix of topsoil and compost rather than topsoil alone.

Tips before you order

• Ask for screened topsoil. It has had stones and roots removed and spreads much more easily.
• Loosen the ground underneath before spreading, so the new soil does not sit on a hard layer.
• Spread and rake the soil, then firm it by walking over it before laying turf or sowing seed.
• Plan where the delivery will be tipped. A large load can block a driveway for a day or two.

Frequently asked questions

How much topsoil do I need for 1,000 sq ft?

About 6.2 cubic yards at 2 inches, 12.3 cubic yards at 4 inches and 18.5 cubic yards at 6 inches, before adding extra for settling.

Can I lay turf on 2 inches of topsoil?

It will take, but 4 inches or more gives much better, drought-resistant results, especially on clay or stony ground.

How much grass seed do I need after the topsoil?

That depends on the seed mix. Our grass seed and turf calculator gives the amount for your lawn size.

Related: the DIY Project Budget & Materials Planner turns your measurements into quantities, costs and a shopping list.

The quick answer: a 12 × 12 ft deck needs 26 deck boards, each 12 ft long, using standard 5.5 inch wide boards with a 1/8 inch gap. Buy 28 boards to allow for a couple of bad boards and cutting mistakes.

Below is the method, a table for other common deck sizes, and a quick guide to joists and screws. For any size or board width, use the deck board calculator, which also works in metres.

How the 26 boards are worked out

1. Find the width each board covers. A board is 5.5 in wide, plus a 1/8 in (0.125 in) gap = 5.625 in.
2. Convert the deck width to inches. 12 ft × 12 = 144 in.
3. Divide. 144 ÷ 5.625 = 25.6, so you need 26 rows of boards.
4. Match board length to the deck. On a 12 ft deck, one 12 ft board covers each row, so 26 boards.
5. Add 5–10%. 26 × 1.08 ≈ 28 boards.

The boards run at right angles to the joists. The last row is usually ripped down to fit, which is why you round up.

Deck boards for other sizes

These figures use 5.5 in boards with a 1/8 in gap, laid straight, before adding any spares.

Deck size	Board length	Rows	Boards needed
8 × 8 ft	8 ft	18	18
10 × 10 ft	10 ft	22	22
10 × 12 ft	12 ft	22	22
12 × 12 ft	12 ft	26	26
12 × 16 ft	16 ft	26	26
16 × 16 ft	16 ft	35	35
20 × 12 ft	12 ft (running the short way)	43	43

If you cannot get boards as long as the deck, stagger the joints so they do not all line up on the same joist. Each joint must land on a joist, with a screw in each board end.

Metric decks

In the UK and Australia, deck boards are commonly around 120–145 mm wide and sold in 2.4 m, 3.6 m and 4.8 m lengths. For a 3.6 × 3.6 m deck using 140 mm boards with a 5 mm gap:

• Cover width per board: 140 + 5 = 145 mm
• Rows: 3,600 ÷ 145 = 24.8, so 25 boards of 3.6 m
• With spares: about 27 boards

Joists for a 12×12 deck

With joists at 16 inch centres, a 12 ft wide frame needs 144 ÷ 16 = 9 spaces, which is 10 joists. Composite boards and diagonal layouts often need joists at 12 inch centres, which means 13 joists. Always check the board maker’s spacing and your local building rules.

Screws and fixings

Face screwing uses two screws at every joist on every board. For a 12×12 deck with 26 boards and 10 joists, that is 26 × 10 × 2 = 520 screws. A rough rule of thumb is 350 screws per 100 sq ft. Buy a pack of at least 600 to cover dropped and snapped screws. Hidden clip systems use one clip per board at each joist instead.

Board gaps: wood vs composite

• Kiln-dried or seasoned timber: gap of about 1/8 in (3–5 mm).
• Wet pressure-treated timber: lay tight or with a very small gap. The boards shrink as they dry.
• Composite: follow the maker’s guide, typically 3/16 in (about 5 mm), with extra end gaps in hot weather.

A bigger gap means each board covers more width, so you need slightly fewer boards. The calculator lets you set your own gap.

Frequently asked questions

How many 16 ft deck boards for a 12×16 deck?

If the boards run the 16 ft length, you need 26 boards of 16 ft, or 28 with spares.

Can I use 2×6 boards instead of 5/4 x 6?

Yes. Both are 5.5 in wide, so the board count is the same. 2×6 boards are stiffer and can span joists up to 24 in apart; 5/4 boards normally need 16 in spacing.

Do I need extra boards for a picture-frame border?

Yes. Add the perimeter of the deck in boards, plus extra blocking so the border boards are supported. For a 12×12 deck that is four extra 12 ft boards.

How many square feet is a 12×12 deck?

144 square feet, or about 13.4 m².

Related: the DIY Project Budget & Materials Planner turns your measurements into quantities, costs and a shopping list.

The quick answer: one ton of gravel covers about 116 square feet at 2 inches deep, or about 58 sq ft at 4 inches. In metric, one tonne covers about 13 m² at 50 mm deep. To find your total, work out the volume of the area and multiply by the weight of the gravel.

This guide shows the formula, how deep to lay gravel for paths and driveways, and a full worked example. For an instant answer, use the gravel and mulch calculator, which gives the result in cubic yards, tons, m³ and tonnes.

Gravel coverage at a glance

The table uses typical densities of 1.4 tons per cubic yard and 1.5 tonnes per m³ for crushed stone and pea gravel. Heavier stone such as granite covers a little less.

Depth	Coverage per ton (US)	Depth	Coverage per tonne (metric)
1 in	230 sq ft	25 mm	27 m²
2 in	116 sq ft	50 mm	13 m²
3 in	77 sq ft	75 mm	9 m²
4 in	58 sq ft	100 mm	6.7 m²
6 in	39 sq ft	150 mm	4.4 m²

The formula

1. Measure the area. Length × width.
2. Multiply by the depth to get the volume. Convert inches to feet (divide by 12) or millimetres to metres (divide by 1,000) first.
3. Convert to cubic yards if you work in feet. Divide cubic feet by 27.
4. Multiply by the density to get the weight: about 1.4 tons per cubic yard or 1.5 tonnes per m³.
5. Add 5–10% for uneven ground and compaction.

Worked example: a gravel driveway

Take a driveway 10 ft wide and 50 ft long with a 4 inch layer of gravel:

• Area: 10 × 50 = 500 sq ft
• Volume: 500 × (4 ÷ 12) = 167 cubic feet
• Cubic yards: 167 ÷ 27 = 6.2 yd³
• Weight: 6.2 × 1.4 = 8.7 tons
• With 10% extra: about 9.5 tons

The same job in metric, for a driveway 3 m wide and 15 m long at 100 mm deep:

• Volume: 3 × 15 × 0.1 = 4.5 m³
• Weight: 4.5 × 1.5 = 6.75 tonnes
• With 10% extra: about 7.4 tonnes

How deep should gravel be?

Project	Recommended depth
Decorative borders and beds	1–2 in (25–50 mm)
Garden paths	2 in (50 mm)
Patio or seating area	2–3 in (50–75 mm)
Driveway top layer	2–3 in (50–75 mm) over a compacted base
Driveway base (crushed stone / MOT Type 1)	4–6 in (100–150 mm)

Going deeper than recommended on a path is a false economy. Loose gravel more than about 2 inches deep is hard to walk on and gets kicked about. For driveways, the strength comes from the compacted base, not from a thick top layer.

Bulk bags, loose loads and small bags

• Bulk (jumbo) bags in the UK usually hold 750–900 kg. A typical 850 kg bag covers around 11 m² at 50 mm.
• Loose loads by truck are sold by the ton, tonne or cubic yard and are the cheapest option for driveways.
• Small bags of 20–25 kg or 0.5 cu ft are fine for a border, but you would need around 40 of them for a single tonne.

Common mistakes

• Forgetting to convert inches to feet before multiplying.
• Ordering the top layer only and forgetting the sub-base.
• Not allowing for compaction: a crushed stone base can settle by 10–15% once rolled.
• Skipping weed membrane under decorative gravel, then losing stone into the soil.

Frequently asked questions

How many square feet does a cubic yard of gravel cover?

About 324 sq ft at 1 inch, 162 sq ft at 2 inches, 108 sq ft at 3 inches and 81 sq ft at 4 inches.

How much does a cubic yard of gravel weigh?

Usually 2,600–3,000 lb, or roughly 1.3–1.5 tons, depending on the stone and how wet it is.

Is pea gravel the same weight as crushed stone?

They are close. Pea gravel is round and does not lock together, so it is better for paths and play areas. Angular crushed stone compacts firmly and is the right choice for driveways.

How much gravel for a 10×10 area?

At 2 inches deep, a 10 × 10 ft area needs about 0.62 cubic yards, or just under 0.9 tons.

Related: the DIY Project Budget & Materials Planner turns your measurements into quantities, costs and a shopping list.

The quick answer: a 10 × 10 ft floor is 100 square feet. With 12 × 12 inch tiles you need 100 tiles, or 110 tiles once you add the usual 10% for cuts and breakages. With larger 12 × 24 tiles it is about 55 tiles.

Below you will find the simple formula, a table for the most popular tile sizes, and how much extra to buy for different layouts. To skip the maths, use the tile calculator, which works in feet or metres and adds waste for you.

Tiles for a 10×10 room at a glance

These figures are for a plain rectangular 10 × 10 ft (100 sq ft, about 9.3 m²) floor laid in a straight pattern.

Tile size	Area per tile	Tiles (exact)	Tiles with 10% extra
12 × 12 in	1 sq ft	100	110
18 × 18 in	2.25 sq ft	45	50
12 × 24 in	2 sq ft	50	55
24 × 24 in	4 sq ft	25	28
6 × 24 in plank	1 sq ft	100	110
300 × 300 mm	0.09 m²	104	114
600 × 600 mm	0.36 m²	26	29

Grout joints of 2–3 mm make each tile cover slightly more floor, but the difference is small. Ignore it and let the waste allowance cover you.

How to work it out yourself

1. Measure the floor. Multiply length by width: 10 ft × 10 ft = 100 sq ft.
2. Work out the area of one tile. Multiply its length by its width in inches and divide by 144. A 12 × 24 tile is 288 ÷ 144 = 2 sq ft.
3. Divide floor area by tile area. 100 ÷ 2 = 50 tiles.
4. Add waste. 50 × 1.10 = 55 tiles. Always round up to a whole tile, then up to a whole box.

If the room is L-shaped, split it into rectangles, work out each area and add them together. Take off any area under fixed kitchen units or a bath, but not under a vanity or toilet, which you tile around.

How much extra should you buy?

The waste allowance depends on the layout and on how many cuts the room needs.

• 10% for a straight (grid) layout in a simple room.
• 15% for a diagonal layout, herringbone or a room with lots of corners, pipes and doorways.
• 20% for large-format tiles in a small, awkward room, where one bad cut can waste a whole tile.

It is also worth keeping a few spare tiles after the job. If one cracks in a few years, the exact colour and batch may no longer be on sale.

Buying tiles by the box

Tiles are usually sold in boxes that cover a fixed area, such as 10.76 sq ft (1 m²) or 16 sq ft. Divide your total area including waste by the box coverage and round up. For 110 sq ft of 12 × 12 tiles in 10 sq ft boxes, that is 11 boxes.

Check the batch or shade number printed on every box. Tiles from different batches can vary slightly in colour, so buy everything at once and mix tiles from several boxes as you lay them.

Don’t forget grout and adhesive

Tile is only part of the order. For a 100 sq ft floor you will also need:

• Tile adhesive or thinset. Coverage depends on the trowel notch. Larger tiles need a bigger notch, so they use more. Check the coverage chart on the bag and add 10%.
• Grout. The amount depends on tile size, joint width and tile thickness. The grout calculator works it out for you.
• Trim and spacers for edges, doorways and to keep joints even.

Common mistakes that leave you short

• Measuring only the main rectangle and forgetting door recesses or alcoves.
• Rounding down at each step instead of rounding up.
• Using a 10% allowance for a herringbone or diagonal pattern.
• Not checking that all boxes are from the same batch.

Frequently asked questions

How many boxes of tile do I need for a 10×10 room?

Take 110 sq ft (100 sq ft plus 10%) and divide by the coverage on the box. With boxes covering 15 sq ft, you need 8 boxes.

Are bigger tiles cheaper to lay?

Bigger tiles mean fewer grout lines and faster laying, but they need a very flat floor and can create more waste in a small room. In a 10×10 room, 12 × 24 is a good middle ground.

How many tiles for a 10×10 wall?

The maths is the same: 100 sq ft of wall needs the same number of tiles as 100 sq ft of floor. Take off the area of any windows or doors first.

Can I use the same numbers for a 12×12 room?

A 12 × 12 room is 144 sq ft, so multiply the figures above by 1.44. With 12 × 12 tiles, that is about 159 tiles including 10% extra.

Related: the DIY Project Budget & Materials Planner turns your measurements into quantities, costs and a shopping list.