Stair Calculator
Calculate riser height, total run and stringer length for a staircase.
Assumptions used in this calculation
- Standard tread depth: Uses a default 10-inch tread depth (run) per step for the stringer length calculation, adjust if your actual tread depth differs.
- Code compliance not checked: Doesn't validate riser height or tread depth against your local building code's minimum and maximum limits, always confirm against local code before building.
About this calculator
A staircase with risers that are even a little too tall or too shallow feels wrong underfoot and can fail a building inspection, yet the geometry behind riser height, total run and stringer length involves more than one calculation to get right. This calculator divides total rise by the number of steps to find riser height, multiplies a standard tread depth by the number of steps to find total run, then applies the Pythagorean theorem to those two figures to find the stringer, the diagonal board that supports each tread. Enter total rise and how many steps you're planning, and it returns all three figures at once instead of you working through the geometry by hand or guessing at a step count that happens to fit. Because comfortable, code-compliant risers generally fall between about 7 and 7.75 inches, checking the resulting riser height against that range before cutting any stringers can save an expensive rebuild.
Worked example
108in rise, 15 steps, 10in tread
Result: Riser height = 7.2in, stringer ≈ 184.8in
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