Stair rise and run calculator
Step count, riser height, total run and pitch angle.
Fill in the fields and the result will appear here automatically.
Divides the total rise of one straight flight into equal risers. Their count rounds up so the actual height does not exceed your chosen limit. The upper landing replaces the last tread, giving one fewer tread than risers. It also shows horizontal run, one-step angle and 2h + b against the selected model range of 0.60–0.65 m; this is not a building-code check.
How it works
Formula and logic
One straight flight: n = ceil(H/hmax) risers, h = H/n, n − 1 treads and horizontal run (n − 1)b. Angle atan2(h, b) describes one-step geometry. Testing 2h + b against 0.60–0.65 m is a chosen model guideline, not building-code approval. H, b and hmax are positive and finite; n is a safe integer. One riser permits zero treads and run. Opening size, headroom and guards are not calculated.
Example
A 2.8 m rise with a 0.18 m limit gives 16 risers of 0.175 m, 15 treads and a 4.2 m run.
Fields and units
- Total rise — m
- Tread depth — m
- Maximum riser height — m
How to use
- — Measure total rise between finished floor levels.
- — Enter tread depth in m.
- — Enter your chosen maximum riser height in m.
- — Check actual height, run and the 2h + b guideline; project requirements need a separate check.
Method and limitations
- Calculation method
- Formula and logic
- Limitation
- This is a geometric quantity calculation within the described model. It does not establish load capacity, safety or project compliance; check design parameters separately.
FAQ
Why is there one tread fewer than risers?
Because the last riser lands on the upper floor, and there is no separate step there.
Why round the step count up?
Rounding down would exceed the entered maximum riser. That is your parameter for this model, not an automatically verified code limit. After ceil, the total height is divided evenly among risers.
What does the 2h + b rule mean?
It is twice the riser height plus tread depth. This product uses 0.60–0.65 m only as a selected step guideline. Falling inside it does not establish code compliance or stair safety.
What pitch angle is normal?
The calculator does not select a code pitch. It shows atan2(riser height, tread), the angle of one step rather than atan(total rise/run), because there is one fewer tread. Check permitted parameters and headroom for the actual project.