A clear result in a few inputs.
- Enter the requested values.Use consistent units and the real values for your scenario.
- Read the main result and breakdown.NumLuma recalculates immediately when an input changes.
- Check the formula and assumptions.Use the supporting context before making a real-world decision.
What this calculator does
Stair geometry connects total vertical rise, number of risers, total horizontal run and tread depth. NumLuma rounds the target riser count to a whole number and then recalculates the actual riser height so every riser in the modeled flight is equal.
What to know before you use the result
- This is planning geometry, not building-code approval.
- Local codes can set maximum riser heights, minimum tread depths, headroom and landing requirements.
- Finished-floor thickness can change the actual total rise.
Common mistakes to avoid
- Using rough-framing rise instead of finished-floor-to-finished-floor rise.
- Assuming the target riser height will remain exact after rounding to a whole number of risers.
- Using one fewer or one more tread without considering the upper floor or landing geometry.
Where this calculation is useful
Deck stairsInterior stairsLayout planningRise/run checks
Related concepts
stair risertread depthtotal risestair run