Stair Carpet Calculator
ConstructionCalculate how much carpet you need to cover a staircase, including treads and risers. Enter step count and dimensions to get square feet and square yards.
Carpet Needed
58.5
Carpet Needed
6.5
What is a Stair Carpet?
A Stair Carpet Calculator determines how much carpet material is needed to cover a staircase, accounting for both the horizontal tread and vertical riser surfaces on each step. Unlike a flat floor area calculation, stair carpeting covers two surfaces per step, which makes manual estimation more error-prone than it first appears.
The calculator converts your step count and dimensions directly into both square feet and square yards, since carpet is commonly priced in the latter unit. If you're finishing other parts of a stairway project, the Ramp Calculator and Decking Calculator cover related sloped-surface and material planning.
How to use this Stair Carpet calculator
- Enter the Number of Steps in your staircase.
- Enter the Step Width in inches (reduce this if calculating for a narrower runner rather than full-width carpet).
- Enter the Tread Depth in inches — the horizontal surface where you step.
- Enter the Riser Height in inches — the vertical face of each step.
- Review the Carpet Needed results in both square feet and square yards to compare against supplier quotes or remnant sizes.
Formula & Methodology
The calculator sums the tread-plus-riser area across all steps: Carpet per Step = ((Tread Depth + Riser Height) × Step Width) ÷ 144 Total Carpet (sq ft) = Carpet per Step × Number of Steps Total Carpet (sq yd) = Total Carpet (sq ft) ÷ 9 Worked example: For a 13-step staircase with 36 in step width, 11 in tread depth, and 7 in riser height: Carpet per Step = ((11 + 7) × 36) ÷ 144 = (18 × 36) ÷ 144 = 648 ÷ 144 = 4.5 sq ft Total Carpet (sq ft) = 4.5 × 13 = 58.5 sq ft Total Carpet (sq yd) = 58.5 ÷ 9 ≈ 6.5 sq yd
Frequently Asked Questions
Stair carpet needs are calculated per step by adding the tread depth and riser height (the two surfaces carpet covers on each step) and multiplying by the step width, then summing across all steps. This calculator handles that calculation and converts the total into both square feet and square yards.
Carpeted stairs typically cover both the horizontal tread (where you step) and the vertical riser (the face of the step) for a finished look, so both dimensions need to be included in the area calculation for each step rather than just the tread alone.
Carpet is most commonly sold by the square yard, though remnant pieces for stairs are sometimes priced by the square foot — this calculator provides both units so you can compare pricing regardless of how your supplier quotes it.
This calculator computes the base area needed to cover treads and risers; for patterned carpet or runners that need to align visually from step to step, add 10-15% extra material to account for pattern matching and cutting waste.
A stair runner covers only a center strip of each tread and riser (commonly 27-36 inches wide) leaving exposed wood or trim on the sides, while full stair carpeting covers the entire step width — this calculator assumes full-width coverage based on your Step Width input, so reduce that input if calculating for a runner instead.
A standard residential staircase with an 8-9 foot floor-to-floor rise typically has 13-15 steps, based on a comfortable riser height around 7-7.5 inches, though this varies by home design and local building code requirements.
This calculator estimates carpet material area only — padding (underlayment) is typically purchased separately and cut to the same tread and riser dimensions, so you can use the same square footage figure for padding estimates as a starting point.
This calculator assumes standard rectangular treads and risers found on straight staircases — curved or spiral stairs have wedge-shaped treads that vary in depth across the width, requiring a more detailed per-step measurement rather than uniform tread depth and step width inputs.
Most carpet retailers price and sell by the square yard, so use the Carpet Needed (sq yd) result directly when requesting quotes or ordering remnant pieces for your stair project.
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