Stair Rise & Run Calculator
Calculate stair riser height, tread depth, step count, total run and stair angle from a total floor-to-floor rise — solving from either a target riser height or a desired step count — with a common building-code comfort check.
Input
The full vertical height being climbed, in the unit selected below.
Solve for the step count from a target riser height, or solve for riser height from a fixed step count.
Preferred riser height; the actual height is recomputed so a whole number of steps fits the total rise.
Output
| Metric | Value |
|---|---|
| No data yet | |
One-line overview of steps, riser, tread, run and angle.
Guides
Building a staircase starts with one number: the total rise, the floor-to-floor height the stairs need to climb. Step count, riser height, tread depth, total run, and how steep the stairs feel all fall out of that measurement plus a comfort rule builders have relied on for generations. This calculator solves in either direction: give it a target riser height and it solves for the step count, or give it a step count and it solves for the riser height.
How it works
- Total rise is the vertical distance from one finished floor to the next. Measure it directly rather than assuming a "standard" story height — it varies with subfloor, joist depth and flooring thickness.
- Step count. Solving from a target riser height divides the total rise by that height and rounds to the nearest whole number of steps — you can't build a fractional step. Solving from a fixed step count uses that number directly.
- Riser height is the total rise divided evenly across that whole step count, which is why the actual riser height can differ slightly from the target entered.
- Tread depth comes from a version of the Blondel comfort rule: two risers plus one tread should land around 25 inches (about 63.5 cm), so tread = 25in − 2 × riser. Taller risers get shallower treads; shorter risers get deeper treads.
- Total run is the horizontal footprint: the number of treads (one fewer than the risers, since the top floor is the final "step") times the tread depth.
- Stair angle is the incline in degrees — the arctangent of riser over tread. Comfortable stairs typically sit in the low-to-mid 30s.
- Code-compliance check flags the result against the comfort band commonly cited for residential stairs: riser roughly 7-7.75 in (178-196 mm), tread roughly 10-11 in (254-279 mm). Since tread is derived from riser, this mostly comes down to whether the riser lands in a workable range.
Both metric (cm) and imperial (in) units are supported.
Reading the result
The table lists step count, tread count, riser height, tread depth, total run, stair angle, the raw "2R + T" comfort figure, and the compliance verdict, with a reason when something falls outside the common band. The summary field packs the same numbers into one copyable line for a cut sheet or a note to a contractor.
Why solve from riser height instead of picking a step count?
Most people start with a riser height in mind — "roughly 7-inch steps" — since that governs how a staircase feels to walk. Solving from riser height finds the closest whole-step count automatically instead of guessing and checking.
What if my riser or tread comes back out of range?
The total rise likely doesn't divide evenly into a comfortable step count at that target riser height. Try nudging the target riser height, or add/remove a step.
Is this a substitute for my local building code?
No. Riser/tread limits, headroom, handrail, and landing requirements vary by jurisdiction and by whether the stair is residential or commercial. Treat the compliance check as a sanity check only — your local building department and adopted code (IRC, IBC, or a regional amendment) are always the final authority.