Carpet Calculator
Find how much carpet to buy for a room from a fixed-width roll, with seams, offcut and cost.
For a rectangular room. Patterned carpet needs extra length to match the pattern at seams, and pile should run the same way on every piece — ask your fitter to confirm before ordering.
About this tool
Enter the room size and the carpet roll width — 4 m or 5 m in the UK and Europe, usually 12 ft in the US. The calculator adds a trimming allowance, tries the roll both ways round, and gives the length to buy, the area you pay for, the number of seams and an optional cost.
Frequently asked questions
Carpet is cut from a roll of fixed width, so you buy a length, not just an area. If the room (plus about 10 cm for trimming) is narrower than the roll, buy the room length plus 10 cm: a 4.5 × 3.5 m room on a 4 m roll needs 4.6 m, which is 18.4 m² of carpet.
In the UK carpet usually comes in 4 m and 5 m widths. In the US most broadloom carpet is 12 ft wide, with some ranges at 13 ft 6 in.
You need two or more pieces joined with a seam. A 6 × 4.5 m room on a 4 m roll needs two drops; laying them across the 4.6 m width takes 2 × 4.6 = 9.2 m, less than 2 × 6.1 = 12.2 m the other way. A 5 m roll would cover it in one 6.1 m piece.
Add at least 10 cm (about 4 in) to each measurement for fitting and trimming against uneven walls. Patterned carpet needs extra length to match the pattern across seams.
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