Stair Calculator
Calculate stair dimensions including number of steps, rise per step, total run, stringer length, and building code compliance check.
Stair dimensions
Updates as you typeMode
What do you want to solve for? ?
Available run ?
—
in
Target angle ?
—
°
Units
Measurement system ?
Rise & run
Total rise ?
—
in
Floor-to-floor height
Run per step ?
—
in
Desired tread depth
Geometry (optional)
Stair width ?
—
in
Tread nosing ?
—
in
Tread thickness ?
—
in
Headroom clearance ?
—
in
Per-step layout
| Step | Cumulative rise | Cumulative run | Riser top elevation | Progress |
|---|
Formula
N
=
round(
total rise
ideal rise
)
rise
=
total rise
N
,
total run
=
(N − 1)
×
run
stringer
=
√(total rise² + total run²)
,
angle
=
atan2(total rise, total run)
- N
- Number of steps (risers)
- Total rise
- Finished floor to finished floor height
- Ideal rise
- Target comfortable step height (~7.5 in / 19 cm)
- Run
- Horizontal tread depth, nosing to nosing
- Stringer
- Diagonal length of the supporting beam
- Angle
- Stair pitch from horizontal, in degrees
Worked example — your numbers
- Ideal rise ≈ —
- N = round(total rise / ideal rise) = —
- Rise per step = total rise / N = —
- Total run = (N − 1) × run = —
- Stringer = √(rise² + run²) = —
- Angle = —
Building codes (IBC, IRC, OSHA) each define their own acceptable range for rise, run, and their sum. The two-to-one rule — 2 × rise + run ≈ 25 in — is a rule of thumb for comfortable stride, independent of code.