stairsClassic tool
Stair Calculator
Estimate risers, treads, total run, angle, and footprint for a straight stair.
Use this stair calculator to sketch a straight stair from total floor-to-floor rise, your target riser height, and tread depth. It gives you a fast way to see how many risers make sense, how far the stair will project into the room, and whether the angle feels closer to a comfortable residential layout or a steeper climb.
Enter the measurements in the same unit you plan to use on site or in your draft layout. If you also add stair width, the tool estimates the floor area the stair footprint consumes. That makes it easier to compare options before you move into detailed drawings or fabrication.
This is a planning reference, not a code check. Always confirm local building rules, finish thicknesses, landings, guard requirements, and structural details before construction.
Use clear inputs to get a more useful result.
How the calculation works
The tool divides total rise by the riser height you want and rounds to a whole number of risers. It then recalculates the exact riser height, assumes one fewer tread than risers for a straight stair, and multiplies tread depth by tread count to estimate total run.
It also applies the common 2 risers + 1 tread stride rule and calculates the stair angle against the floor. Together, those values help you judge comfort, steepness, and footprint.
How to read the result
- Risers: vertical climbs from the lower floor to the upper floor.
- Exact riser height: real riser size after rounding.
- Total run: horizontal space needed by the straight stair.
- Stride rule: a quick comfort check based on riser and tread proportions.
If the stair reads as too steep, try a lower target riser, a deeper tread, or a landing. If the footprint grows too much, compare alternate layouts before locking the plan.