Carpet Calculator: Square Yards & Padding
Work out how much broadloom carpet and padding you need, using the standard 12-foot or 15-foot roll width, plus stairs and installation supplies.
Carpet is sold by the square yard (9 sq ft) from rolls 12 or 15 feet wide. A 14 × 11 ft room cut from a 12-ft roll needs about 19.3 square yards (174 sq ft), because you pay for the full roll width plus trim, not just the room area.
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How to calculate carpet
Carpet comes in rolls 12 or 15 feet wide, and you buy a length cut from the roll. That means the carpet you buy is usually larger than the room: you pay for the full roll width even if the room is narrower.
otherwise: area × 1.1 plus seam allowance
square yards = square feet ÷ 9
This calculator tries both orientations of the room and chooses the one that uses less carpet. When the room is wider than the roll, a seam is needed, which adds waste and requires careful placement away from heavy traffic.
Carpet needed for common rooms (12-ft roll)
| Room size | Room area | Carpet to buy (sq ft) | Sq yd |
|---|---|---|---|
| 10 × 10 ft | 100 sq ft | 126 | 14.0 |
| 10 × 12 ft | 120 sq ft | 150 | 16.7 |
| 12 × 12 ft | 144 sq ft | 164 | 18.3 |
| 12 × 15 ft | 180 sq ft | 204 | 22.7 |
| 12 × 18 ft | 216 sq ft | 244 | 27.1 |
| 14 × 16 ft | 224 sq ft | 252 | 28.0 |
Padding, tack strip and stairs
Padding is cut from the room's actual area (no roll offcut), so it's usually less than the carpet quantity. Standard pad is ⅜ to ½ inch thick; use thin, firm pad under Berber and loop styles. Tack strip runs around the room perimeter. Stairs take roughly 1 square yard per 3 steps for standard 36-inch stairs, plus waterfall landings.
Carpet vs. other floors
For hard floors by the box, use the flooring calculator; for ceramic and porcelain, the tile calculator. Measure irregular rooms with the square footage calculator.
Frequently asked questions
How do I calculate square yards of carpet?
Multiply the length and width of the room in feet to get square feet, then divide by 9. Add extra for the roll width, trim and any seams.
How much carpet do I need for a 12×12 room?
A 12×12 room (144 sq ft, 16 sq yd) usually needs about 18 square yards with a 12-ft roll, because the width plus trim forces a seam. A 15-ft roll avoids the seam but buys about 21 square yards.
How much extra carpet should I buy?
Plan for 10% more than the room area on average, but the roll width often determines the real amount.
How wide is a roll of carpet?
Standard broadloom rolls are 12 feet wide; many styles come in 15 feet, and some in 13.5 feet.
Do I need padding under carpet?
Yes. It adds comfort, absorbs sound and protects the carpet from wear. Most carpet warranties require it.
How much carpet for stairs?
About 1 square yard per 3 steps for standard-width stairs; add for landings and waterfall edges.
How much does carpet cost per square yard?
Carpet commonly costs roughly $15–$60 per square yard for materials depending on fiber and quality, before padding and installation.
Can I carpet over tile or hardwood?
Yes, with tack strips and padding, though tile and hardwood are often preferable to preserve.
Sources and further reading
- The Carpet and Rug Institute — CRI: carpet installation standards
These references support the general guidance on this page. The calculator applies the standard formulas shown above to the numbers you enter.
Related calculators
. Estimates only. Always confirm quantities with your supplier or a qualified contractor before ordering, and add extra for waste and site conditions.