Stair Carpet Calculator
How much carpet or runner for stairs: tread, riser and nosing per step, total strip length, wall-to-wall carpet area or runner length, padding, stair rods and cost.
How it works
per step = tread + riser + nosing wrap (2.5 cm / 1″) · strip length = steps × per step + 5 cm (2″) at top and bottom · area = length × width × (1 + waste)
Each step takes carpet over the tread, down the riser and around the nosing, so measure one step that way (a flexible tape helps) and multiply by the number of treads; about 2.5 cm (1″) wraps the nosing. Wall-to-wall stair carpet is usually cut from a 4 m (12 ft) roll and priced by area, while a runner is bought by length in its own width and leaves an even margin of wood showing each side — typically 7–10 cm (3–4″). Add 10% for fitting, more for a patterned runner that must line up on every step, and count landings separately.
Worked example
13 steps with 28 cm treads and 18 cm risers take 28 + 18 + 2.5 = 48.5 cm of carpet per step; 13 × 48.5 + 10 cm for the top and bottom = 6.41 m of strip. Wall-to-wall at 90 cm wide with 10% waste that is 6.41 × 0.90 × 1.10 = 6.34 m² of carpet, costing $158.52 at $25 per m², plus 3.57 m² of padding for the treads.
Sources: Carpet and Rug Institute — installation standard CRI 105 · ICC — IRC R311.7 stairways (tread and riser limits)
Frequently asked questions
How do I measure stairs for carpet?
Measure tread depth plus riser height plus about 1″ (2.5 cm) for the nosing wrap, multiply by the number of steps, and multiply by the stair width. Measure each step if they differ, and add the landing as a separate rectangle.
How much carpet do I need for 13 stairs?
With 28 cm treads, 18 cm risers and a 90 cm wide stair, 13 steps take about 6.4 m of strip, or roughly 6.3 m² of carpet with 10% waste (about 68 sq ft).
How wide should a stair runner be?
Leave 7–10 cm (3–4″) of wood showing each side: a 90 cm (36″) stair usually takes a 68–76 cm (27–30″) runner.
Do I need padding on stairs?
Yes, but only on the treads and over the nosing, not the risers. Use a dense, thin pad (under 1 cm / ⅜″) so the carpet grips the nosing safely.
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This calculator is for educational purposes. Double-check important results before acting on them.