Tool

Stair Calculator

Enter the total height you need to climb (floor to floor). I'll lay out the stairs — steps, riser height, tread depth, the stringer length to cut, and the angle — with a diagram.

0

steps (risers)

0"

riser height

0"

tread depth

0"

stringer length

0

treads

0"

total run

0°

angle

Pouring it in concrete?

Add the stair width and I'll work out the concrete to order.

Concrete needed

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80 lb bags

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60 lb bags

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40 lb bags

Solid steps poured on grade. Add ~10% for waste. For a big pour, ready-mix is usually cheaper.

How it works

  1. Number of risers = total rise ÷ target riser, rounded to a whole number.
  2. Exact riser = total rise ÷ number of risers (so every step is equal).
  3. Treads = risers − 1. The top "tread" is the landing.
  4. Tread depth uses the carpenter's rule 2 × riser + tread ≈ 25" unless you type your own.
  5. Total run = treads × tread depth (the run per step). The nosing is an overhang on the front edge, so it doesn't change the run.
  6. Stringer length = √(total rise² + total run²) — the diagonal board you cut.
  7. Angle = atan(total rise ÷ total run). A comfortable stair sits around 30–37°.

Common code limits (US IRC): riser ≤ 7¾", tread ≥ 10". Always check your local code.

Concrete steps add up each step as a stacked block — width × run × rise × (N × (N+1) ÷ 2) — which is the volume shown above when you enter a width. For slabs, footings or columns, use the concrete calculator →