Stair Carpet Calculator – How Much Carpet for Stairs? | CalcLoft
Find out how much carpet you need for your stairs in seconds — enter the number of steps, tread depth, riser height and stair width for an instant sq ft and sq yd estimate.
How to measure a staircase for carpet
Each step takes a strip of carpet equal to the tread depth plus the riser height, measured along the slant of the stairs. So the length you need is simply:
Strip length = number of steps × (tread depth + riser height)
For the area, multiply that strip length by the stair width. A typical 11-in tread with a 7-in riser eats 18 in — 1.5 ft — of carpet per step, so a 36-in-wide (3 ft) staircase uses 1.5 × steps × 3 sq ft of tread-and-riser surface. Add about 10% for waste from trimming the edges, fitting the nosing and matching any pattern.
Most carpet comes on 12-ft-wide rolls (144 in). Because standard stairs are only 27–48 in wide, one continuous strip cut the full length of the roll covers the whole staircase with no seams.
How much carpet for 13 stairs?
Using the defaults above — 11-in tread, 7-in riser, 36-in-wide stairs — 13 steps need a strip of 13 × 1.5 = 19.5 ft. That strip covers 19.5 × 3 = 58.5 sq ft (6.5 sq yd) before waste. Add the default 10% and the strip becomes about 21.5 ft, so you should order roughly 65 sq ft — about 7.2 sq yd. Run your own tread and riser sizes through the calculator above for an exact figure.
How much carpet for common staircases?
| Steps | Strip needed* | 27-in wide stairs | 36-in wide stairs |
|---|---|---|---|
| 10 | 16.5 ft | 37 sq ft (4.1 sq yd) | 50 sq ft (5.5 sq yd) |
| 13 | 21.5 ft | 48 sq ft (5.4 sq yd) | 65 sq ft (7.2 sq yd) |
| 15 | 24.8 ft | 56 sq ft (6.2 sq yd) | 74 sq ft (8.3 sq yd) |
| 20 | 33.0 ft | 74 sq ft (8.3 sq yd) | 99 sq ft (11.0 sq yd) |
*Continuous strip along the stringer including 10% waste, based on an 11-in tread and 7-in riser. Landings, winders and open treads add extra — measure them separately and add the result.
Related guides
Stair carpet calculator FAQ
How much carpet do I need for 13 stairs?
For 13 steps with an 11-in tread and 7-in riser on a 36-in-wide staircase you need about 65 sq ft — roughly 7.2 sq yd — including 10% waste. On narrower 27-in stairs, about 48 sq ft (5.4 sq yd).
How do I measure stairs with a landing or a turn?
Measure each straight run separately using the steps in that run, then add the landing as its own rectangle of length × width. L-shaped and winder stairs need a piece for every direction change — count the winders in their run and expect extra waste where carpet turns.
Is a 12-ft-wide roll of carpet enough for my stairs?
Yes for standard stairs. A 12-ft roll is 144 in wide, and stair widths are usually 27–48 in, so a single strip runs the full length with no seam. You only need to seam or special-order if your stair or landing is wider than the roll.
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