calcs.homes

Stair calculator

Enter the total rise between floors and this stair calculator works out riser height, number of risers, total run, and stringer length.

Total risei
in
Desired riser heighti
in
Tread depth (run)i
in
Result
Number of risers14
Actual riser height7.71 in
Total run10.83 ft
Stringer length14.08 ft

Estimate only — check local code for max riser height and min tread depth.

How stair layout math works

We divide total rise by your desired riser height and round to a whole number of risers, then spread the rise evenly across them for the actual riser height. Total run is tread depth times one fewer than the number of risers (the top step is the landing). Stringer length is the diagonal from the bottom of the stairs to the top, found with the Pythagorean theorem.

Frequently asked questions

Divide your total rise by a comfortable riser height (7-7.5 in / 18-19 cm is typical) and round to the nearest whole number — that's your riser count.

You can't have a fractional riser, so we round to a whole number of risers first, then divide the total rise evenly across them — that gives a slightly different (but consistent) riser height.

The stringer is the diagonal board that supports the treads. Its length is the hypotenuse of the total rise and total run — order lumber at least this long, plus extra for the top and bottom cuts.