Stair Calculator
Risers, treads, stringer length & angle
Designing a staircase or deck steps? Enter the total rise (floor to floor) and your tread depth to get the number of steps, the exact riser height, total run, stringer length and stair angle.
Stair rise, run and riser height
Total rise is the vertical distance from one finished floor to the next. Divide it by a comfortable riser height (around 7–7.5 inches) and round to a whole number of risers — that gives the exact height of each step. The number of treads is always one less than the risers, because the top floor itself is the last step up.
Stair building code basics
Most residential codes cap riser height at 7¾ inches and require a tread depth of at least 10 inches. Risers must be uniform — a variation over 3⁄8 inch between steps is a trip hazard and a common inspection failure. The calculator flags a riser height above the typical code maximum so you know to add a step.
Stringer length and laying out cuts
The stringer is the diagonal board the steps are cut into. Its length is the hypotenuse of the total rise and total run, so a taller or longer stair needs a longer board — use the stringer figure to buy stock long enough before you start notching. Mark each rise and run with a framing square to lay out the steps.
Stair Calculator: frequently asked questions
What is a comfortable stair riser height?
Around 7 to 7.5 inches. Building codes typically allow up to 7¾ inches; lower risers feel easier to climb.
How many steps for an 8-foot floor height?
A floor-to-floor rise of about 105–110 inches usually needs 14–15 risers at roughly 7.5 inches each. Enter your exact rise for the precise count.
How long should a stair stringer be?
It's the diagonal of the total rise and run. For a typical one-story stair, plan on stringer stock of 12–14 feet; the calculator gives the exact length.