Stair Calculator: Riser Height, Tread & Run | Freetulz

Estimate a straight staircase layout from three measurements: total story rise, target riser height, and tread depth. The calculator returns a whole number of risers, the resulting equal riser height, and the horizontal run.

How to use the stair calculator

1. Enter the vertical distance between finished floor levels in inches as the total story rise.
2. Enter your target riser height in inches.
3. Enter the tread depth (horizontal run per tread) in inches.
4. Select Calculate Stair Layout to see the riser count, actual riser height, and total horizontal run.

How the results are calculated

The number of risers is the total rise divided by the target riser height, rounded to the nearest whole number. Actual riser height is total rise divided by that count. The tool assumes the upper floor acts as the final landing, so it estimates one fewer tread than risers. Horizontal run equals (riser count minus one) times tread depth.

For example, a 108-inch rise, 7.5-inch target riser, and 10.5-inch tread depth produce 14 risers, an actual riser height of about 7.71 inches, and 136.5 inches of horizontal run.

Planning notes

This is a dimensional estimate for a straight stair. It does not calculate stair width, headroom, landings, nosings, stringer cuts, materials, or building code compliance. Verify measurements and local requirements with a qualified professional before construction.

Frequently asked questions

Why is actual riser height different from my target?

Riser count must be a whole number. The tool divides the total rise equally among the rounded riser count.

Why is there one fewer tread than risers?

The calculation treats the upper floor as the final landing. Other stair layouts may need a different tread count.