About the Carpet Calculator
Carpet Calculator works out how much carpet to buy for a rectangular room. Enter the room's length and width (in feet or metres) and the width of the carpet roll, add an allowance for cuts and pattern matching, and the page shows the length to buy off the roll, the number of strips, the room area in square feet or metres and square yards, and, if you enter a price per square yard, an estimated cost. It lays the strips along whichever direction needs less carpet. Use it to compare quotes and to avoid buying too little, but ask the shop to check the measurements before you order.
Updated October 2026
How to use the Carpet Calculator
- 1Choose feet or metres and enter the room length and width.
- 2Enter the width of the carpet roll; 12 ft (3.66 m) is the usual width.
- 3Set an allowance for waste, 10% is common.
- 4Add the price per square yard to see the cost.
- 5Read how much to buy and take the numbers to your supplier.
How carpet is sold
Carpet is cut from a wide roll, so you pay for the full width times the length you take, even if your room is narrower. If your room is 15 feet by 12 feet and the roll is 12 feet wide, you buy 15 feet of roll plus a little extra. A room 14 feet wide needs two strips, which means joining them with a seam.
Reducing waste
The calculator tries both directions and chooses the one that uses less carpet. Where there is a choice, the fitter will also think about where seams are least visible and where foot traffic is heaviest. You can sometimes save by using a different roll width or by using leftover pieces in a closet.
- Measure the widest and longest points of the room
- Check door openings and alcoves
- Ask about seam positions
- Keep offcuts for repairs
Before you buy
Measure twice and write down the sizes. Ask the shop to remeasure and quote the fitting, the underlay and removal of old flooring. If you compare carpets, compare the price per square yard and the total. For other flooring use the Flooring Calculator, the Tile Calculator and the Area Converter.
Related tools
Compare with the Flooring Calculator, the Tile Calculator and the Paint Calculator for the walls. The Area Converter changes square feet to square metres.
Features
- Feet or metres
- Strips laid in the cheaper direction
- Waste allowance
- Square yards and area
- Optional cost estimate
- Private: nothing is uploaded
Frequently asked questions
How much carpet do I need for a room?
Multiply the length by the width for the area, then add about 10% for cutting and fitting. Because carpet comes in rolls of a fixed width, you buy by the length of the roll, which the calculator works out.
What width are carpet rolls?
Most are 12 feet (3.66 m) wide. Others are 13 ft 2 in (4 m), 15 ft (4.57 m) or 5 m, depending on the country and the maker.
Why is the amount I buy more than the room area?
The roll is a fixed width, so any part of the width that you do not use is waste. Rooms wider than the roll also need seams.
How do I convert square feet to square yards?
Divide by 9. A room of 180 sq ft is 20 sq yd.
Do I need extra for stairs or patterns?
Yes. Stairs need their own measurements, and patterned carpet may need an extra length to match the pattern at seams. Ask your supplier.
What about underlay (padding)?
The underlay covers the room's floor area, usually without the waste. Use the area of the room shown here.
Does it work for rooms that are not rectangles?
Split the room into rectangles, calculate each one and add them, or ask a fitter to measure.
Is it free to use?
Yes, and nothing is uploaded.