Enter the total rise (floor-to-floor height) along with your desired riser height and tread depth to calculate the number of steps, actual riser height, total run and stringer length.
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The number of steps is your total rise divided by your desired riser height, rounded to the nearest whole number, since you can't have a fractional step. That rounding means the actual riser height (total rise ÷ number of steps) usually differs slightly from your desired height, this calculator shows you the real figure so every step comes out even.
Total run is the tread depth multiplied by the number of treads (one fewer than the number of steps, since the top step is the landing or floor itself). Stringer length is the diagonal distance from the bottom to the top of the stair run, found using the Pythagorean theorem on the total rise and total run.
Most residential building codes call for a riser height between 7 and 7.75 inches and a tread depth of at least 10 inches, aiming for a comfortable stride. Always check your local building code before finalizing a staircase design.
For a total rise of 108 inches, a desired riser height of 7 inches, and a 10 inch tread depth: number of steps = round(108 ÷ 7) = round(15.43) = 15. Actual riser height = 108 ÷ 15 = 7.2 inches (slightly taller than the 7 inch target, so the rise divides evenly). Number of treads = 15 − 1 = 14 (the top step is the landing itself). Total run = 14 × 10 = 140 inches. Stringer length = √(108² + 140²) = √(11,664 + 19,600) = √31,264 ≈ 176.82 inches. Stair angle = arctan(108 ÷ 140) ≈ 37.65°.
Treating the entered 'desired' riser height as the final answer, this calculator rounds to a whole number of steps first, then recalculates the actual riser height so every step comes out exactly even, the actual figure (not your original entry) is what to build to.
Forgetting the number of treads is one less than the number of steps, the top step is the landing or floor itself, not an additional tread, using the step count directly for tread material would overcount by one.
Skipping a local building code check, most residential codes call for a riser height roughly 7 to 7.75 inches and a tread depth of at least 10 inches, this calculator computes the geometry but doesn't verify your specific inputs against any code.
Riser height is adjusted slightly so the total rise divides evenly across a whole number of steps, this keeps every step the same height, which is both safer and typically required by code.
Total rise is the straight-up vertical height. Stringer length is the diagonal length of the support board running under the stairs, which is longer than the rise since it also accounts for the horizontal run.
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