Carpet Calculator

How to calculate how much carpet you need

Carpet is cut from a roll, so you pay for the roll width as well as the room. Measure each room, then work out how many strips of roll it takes and how long each one is.

Each room can run its strips along the length or along the width. The calculator tries both and keeps the one that uses the least roll. If they tie, it keeps the one with fewer seams. Every room is cut on its own, so leftovers from one room are not counted toward the next. You can type measurements in feet, inches, yards or meters, or as a tape-measure reading like 12'6" or 12 ft 6 in.

What width does carpet come in?

The Carpet and Rug Institute, the carpet industry association, says broadloom carpet can be 12 feet, 13.5 feet or 15 feet wide. It also lists six foot carpet. Shaw Floors, a manufacturer, shows a construction width of 12 feet on its “Solidify I 12'” style, and the width filter on its carpet page offers 12 foot and 15 foot styles. We checked these pages in October 2026. The width depends on the style, so confirm it before you order. If your roll is something else, choose “Other width”.

Example: a 15 ft by 20 ft room

The room is 15 feet by 20 feet and the roll is 12 feet wide. A 12 foot strip does not cover 15 feet, so the room needs two strips and one seam. The question is which way to run them.

The floor is 15 × 20 = 300 square feet, or 33.33 square yards. The better layout buys 360 square feet, so 60 square feet (6.67 square yards) is left over after cutting. If your installer asks for 10% extra on the length, 30 × 1.10 = 33 feet of roll, which is 396 square feet or 44 square yards. Type 10 in the extra box to see it.

Carpet needed for common room sizes

Square yards to buy for one room with no trim allowance and no extra, from a 12 foot roll and from a 15 foot roll.

Notice that a wider roll does not always use less carpet. A 15 foot roll uses less for the 15 × 20 room and needs no seam, but it uses more for the 10 × 10 room. For the floor area alone, without roll width, use the square footage calculator.

Tips for measuring and ordering

• Measure the widest and longest points. Rooms that are not square, with bays or alcoves, need the largest size in each direction. Add closets as separate rooms.
• Split L-shaped spaces. Enter each rectangle as its own room. Because every room is cut on its own, the result is a safe upper estimate. Your installer may find a smarter cut.
• Think about seams. The result counts the seams for you. Ask the installer where they would put them.
• Ask about pattern. Patterned carpet may need more length to line up at the seams. Use the extra box for the allowance your seller gives you.
• Compare in the same unit. Sellers quote per square foot or per square yard. The result shows both, and this page shows no prices because they change.
• Padding and stairs. Ask your seller about the pad and the stairs. This calculator does not count them.

Frequently asked questions