Enter your room size and get the square yards of carpet to buy — including waste for seams, doorways and stairs.
Measure the room's length and width in feet and multiply them for the square footage. Add waste — 10 percent for a simple room, more if there are seams or stairs. Carpet is priced by the square yard, so divide the total square feet by 9 to get the square yards to buy.
There are 9 square feet in a square yard, so just divide your square footage by 9. A 180 square foot room with 10% waste is 198 square feet, which is 22 square yards. Carpet stores quote prices and roll sizes in square yards, so this is the number you'll want when you shop.
Carpet comes in fixed roll widths — often 12 feet — so a room that doesn't divide neatly leaves offcuts you pay for but can't use. Add extra to match patterns across seams and to run carpet into doorways and closets. Stairs use noticeably more, so bump the waste toward 20 percent for them.
This is a planning aid. Roll widths and layout drive real waste, which can run higher on odd rooms — always confirm measurements with your installer and round up.