Planning a staircase by hand: risers, steps and run
A staircase is designed backward from one comfort number: a riser (the height of each step) close to 7.5 inches. Too tall and climbing it is tiring; too short and it feels like a ramp with one trip hazard. Everything else — how many steps, how far the staircase runs — follows from that one target and the total vertical rise you're covering.
The method
- Measure the total rise: the vertical distance from the lower floor to the upper floor, in inches.
- Divide the total rise by the 7.5-inch target and round to the nearest whole number — that's the step count. You can't build a fractional step.
- Divide the total rise by that step count to get the exact riser height each step will actually use.
- Multiply (steps − 1) by your chosen tread depth to get the total horizontal run. It's steps minus one because the top step lands on the upper floor itself, so the staircase only needs a tread for every step below that.
In one line: steps = round(rise ÷ 7.5), then riser = rise ÷ steps and run = (steps − 1) × tread.
A worked example
Total rise of 112 inches (a common floor-to-floor height), tread depth of 10 inches.
- Step count:
112 ÷ 7.5 = 14.93, rounds to 15 steps. - Exact riser:
112 ÷ 15 = 7.47 inches— close to the 7.5-inch target, which is the point of rounding to a whole step count first. - Run:
(15 − 1) × 10 = 140 inches, or just under 11.7 feet of floor space.
A second example
A shorter rise of 98 inches, same 10-inch tread.
- Step count:
98 ÷ 7.5 = 13.07, rounds to 13 steps. - Exact riser:
98 ÷ 13 = 7.54 inches. - Run:
(13 − 1) × 10 = 120 inches, exactly 10 feet.
Notice the riser comes out slightly different each time — 7.47 inches versus 7.54 inches — even though both started from the same 7.5-inch target. That's expected: the target picks the step count, and the step count then fixes the exact riser for that specific total rise. You cannot hit 7.5 inches on the nose unless the total rise happens to divide evenly by it.
Why round the step count before dividing
If you instead divided rise by 7.5 and kept the decimal — "14.93 steps" for the first example — you'd have no way to actually build it; a staircase has a whole number of steps or it doesn't exist. Rounding first, then dividing the rise by that whole number, is what keeps every step on a real staircase the same height. An uneven last step is one of the most common tripping hazards in home stairs, and it usually comes from skipping this order of operations.
What this doesn't replace
Building codes set hard limits on riser height, tread depth, headroom and handrail requirements, and those limits vary by jurisdiction and by whether the stair is for a main living area, a deck, or a basement. This method gets you a comfortable, buildable starting layout; checking it against your local code before cutting any lumber is not optional.
The free Stair Calculator runs this same arithmetic from your total rise and tread depth.