Carpet Calculator
Use this carpet calculator to turn room sizes into square feet, square yards and the linear feet of broadloom roll to order. Unlike a box-flooring estimate, carpet is cut from a roll of fixed width, usually 12 ft, so each room is laid along the roll in the direction that uses the least length, and you see the seams that creates. Add stairs, carpet pad, an allowance and prices for a total. For boxed planks use the flooring calculator, and for tile, floor area and paint see the tile, square footage and paint calculators.
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Stairs (optional)
Roll length to order (with allowance)
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Floor area
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Carpet to buy
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Roll length needed (before allowance)
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Seams in the rooms
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Stair carpet area
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Carpet pad
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Estimated cost
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Carpet is cut from a roll of fixed width. For each room the calculator tries both directions: strips = room dimension across the roll ÷ roll width, rounded up; roll length = strips × the other dimension; it keeps the shorter result, and seams = strips − 1. Broadloom is most often 12 ft wide, also made in 15 ft, and some lines come in 13 ft 2 in. Carpet to buy = roll length × roll width after the allowance for waste and seams (10% is a commonly used allowance you can change). Stairs are added by cut area: each step needs tread + riser + nosing in length across the stair width; the defaults (10 in tread, 7.5 in riser, 1 in nosing, 36 in wide) are typical placeholders, so measure your stairs. Pad is counted at the floor area. Pile direction, pattern match and room shape can add waste; ask your installer to confirm the layout.
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How it works
- How do I calculate carpet for a room?
- Multiply length by width in feet for square feet and divide by 9 for square yards. A 12 × 15 ft room is 180 sq ft, or 20 sq yd. Then check the roll: with a 12 ft roll the 12 ft side fits across, so you need 15 linear feet of roll and no seam. Add an allowance for waste before you order.
- Why do I need linear feet of roll and not just square yards?
- Carpet is sold from a roll of fixed width, so you pay for the full width of every length you cut. A 20 × 15 ft room is 300 sq ft (33.3 sq yd) but needs 30 linear feet of a 12 ft roll, which is 40 sq yd to buy, because most of the second strip is cut away. A 15 ft roll would need only 20 linear feet (33.3 sq yd) with no seam.
- How are seams counted?
- Whenever a room is wider than the roll, the carpet is joined along a seam, and the calculator counts strips − 1 per room as a guide. Installers choose the seam locations and may use a different layout, so treat the seam count as an estimate.
- How much carpet do stairs need?
- A common method is to add tread depth + riser height + nosing for one step and multiply by the number of steps and the stair width. With a 10 in tread, 7.5 in riser and 1 in nosing, 13 steps that are 36 in wide need about 60 sq ft, or 6.7 sq yd, before the allowance. Measure your own stairs, because the defaults are only placeholders.
- How much extra carpet should I order?
- A 10% allowance is commonly used for waste, seams and cuts, and the Waste % field starts there; patterned carpet, odd-shaped rooms and stairs can need more. Pad is bought for the floor area. Ask your installer for their own layout before you order.