Stair Carpet Calculator

The amount of carpet a staircase needs depends as much on the installation style as on its size, because the style decides how the carpet wraps each step:

• Waterfall drapes the carpet straight down the face of each riser in one continuous sheet. It is the fastest install and the most economical on carpet — Stairs Calc adds only a small (~½″) nosing‑wrap allowance per step.
• Cap (Hollywood) upholsters each tread and wraps the carpet around and under the nosing, often tucking it down the sides. It gives a tailored, custom look but uses more carpet, so the per‑step allowance is larger (~1½″).
• Standard follows the nosing in the common middle‑ground way, sitting between the two (~1″).

For each step the calculator adds the riser, the run and the style’s wrap to get the per‑step runner length, multiplies by the number of steps, and then adds a 5% waste margin before converting to linear yards and square yards.

You only need a few measurements, and the runner length is the one that matters most. A handy rule of thumb is about 19″ of runner per step — roughly one riser plus one tread plus the nosing — so a 16‑step staircase needs on the order of 25 ft of runner before waste. To measure your own stairs:

1. Count the number of steps (risers) in the flight.
2. Measure one riser height and one tread run, plus the nosing overhang — they are consistent on a code‑built staircase.
3. Decide your runner width. Most runners are 27″–32″ wide, leaving a few inches of tread showing on each side; a full‑width carpet covers the whole tread.
4. For winder or pie‑shaped steps, measure at the widest point — the carpet has to cover the full wedge — and add the nosing wrap so turning steps are not shorted.

Enter those numbers above and Stairs Calc returns the total runner length, the linear yards to buy (with 5% waste), the square‑yard area for your chosen width, and the per‑step length. For hard flooring, tile or paint instead, the stairs square footage calculator reports tread, riser and stringer surface area.