Start with the right measurement
Stair layout is a sequence of equal rises and treads between two finished elevations. This tool helps compare a target riser with the available height; it does not choose a universally legal stair design.
How to use this calculator
- 01Total rise: Finished-floor-to-finished-floor vertical height.
- 02Maximum riser: A planning target used to calculate an equal riser count.
- 03Tread depth: Horizontal going for each tread.
The output separates actual riser height, tread count, total run, stringer length, and stair angle so you can compare layout options before framing.
Units: Use inches or centimetres consistently. Measure to the finished surfaces that people will walk on, not only rough framing.
How the calculation works
Risers = ceiling(total rise ÷ maximum riser). Actual riser = total rise ÷ risers. Treads = risers − 1.A 108-inch rise with a 7.75-inch maximum produces 14 risers at about 7.71 inches.
Worked examples
Basement stair check
- Measure 102 in from finished lower floor to finished upper floor.
- Set maximum riser to 7.5 in: 102 ÷ 7.5 = 13.6, so round up to 14 risers.
- Divide 102 by 14.
Result: Each riser is about 7.29 in; with a 10 in tread, the total run is about 130 in.
Space-constrained layout
- Use 84 in total rise and a 7 in target maximum.
- 84 ÷ 7 = 12 risers, giving a 7 in actual riser.
- If 10 in treads are selected, 11 treads require 110 in of run.
Result: The geometry fits the stated inputs, but landing, headroom, handrail, and local rules still need checking.
How to measure
- 01Measure finished-floor to finished-floor vertically.
- 02Use the intended finished tread depth, not rough framing alone.
- 03Reserve space for landings, headroom, nosings, and handrails before finalizing.
Common mistakes to avoid
- Measuring to unfinished surfaces
- Confusing risers with treads
- Assuming a calculation guarantees compliance
Safety note
Stairs are a fall hazard during construction. Use temporary edge protection and do not rely on an unfinished stringer as a safe access route.
Limits of this estimate
Building codes and structural requirements vary. Confirm dimensions, landings, headroom, guards, and construction with your local authority and a qualified professional.
Frequently asked questions
Why is there one fewer tread?
The upper floor usually serves as the final walking surface.
Are these stairs code compliant?
The calculator cannot determine that; verify every requirement locally.