Carpet is cut from rolls of a fixed width, so you often buy more than the room area. Enter your room size and roll width to see the length to cut, the carpet area you will pay for, and the underlay and gripper rod you need.
Your shopping list
How to measure
- Measure the length and width of the room at the widest points, including into door frames and bay windows.
- Choose the roll width your store sells. 12 ft and 15 ft are common in the US and Canada; 4 m and 5 m in the UK and Australia.
- If the room is wider than the roll, the calculator adds extra strips and joins.
The formula
Strips = room width ÷ roll width (round up) Length to cut = strips × (room length + trim) Carpet to buy = length to cut × roll width
Worked example
A 15 × 12 ft room with a 12 ft roll needs one strip. Add 4 in for trimming: 15.33 ft × 12 ft = 184 sq ft of carpet, for a room of 180 sq ft.
Tips before you buy
- Run the pile in the same direction across the room so the colour looks even.
- Place any seams away from doorways and busy walkways.
- Ask the store to cut the carpet slightly long; it is trimmed to fit at the walls.
Frequently asked questions
Why do I need more carpet than my room area?
Carpet comes in fixed roll widths. You pay for the full width of the roll, plus a little extra length for trimming at each wall.
How much underlay do I need?
The room area plus about 5% for trimming. Underlay is sold in rolls by area.
What is gripper rod?
Gripper rod (tack strip) is nailed around the edge of the room to hold the carpet tight. You need enough to go around the perimeter, less doorways.
Results are estimates for planning only. Always check quantities with your supplier before you buy.