Enter your total floor-to-floor rise and get the number of steps, the exact riser height, the tread run and the stringer length — all checked against the IRC stair code.
Every staircase starts from one number: the total rise, the finished floor-to-floor height. Divide it by a comfortable target step height — around 7 to 7.5 inches — and round to the nearest whole number to get your number of risers (steps). Then divide the total rise by that count to get the exact riser height, so every step is identical. A stair always has one fewer tread than risers (the top floor is the last "step up"), and the total run is the number of treads times the tread depth.
The stringer is the sawtooth board the treads and risers sit on, and it runs along the diagonal of the whole staircase. Its length is the square root of the total rise squared plus the total run squared — straight-up Pythagoras. Round it up to the next standard board length, then lay out and cut the notches from that. Wider stairs need more stringers spaced across the width.
Under the International Residential Code (IRC R311.7), the maximum riser height is 7¾ inches, the minimum tread depth is 10 inches, and you need at least 6 ft 8 in of headroom. A comfortable stair also follows the 2R + T rule: twice the riser plus the tread should land between about 24 and 25 inches. This calculator flags any riser or tread outside the IRC limits and shows your 2R+T figure — but codes vary locally, so always confirm with your building department.
This is a planning aid, not an engineering or code document. It assumes equal risers and a straight flight; landings, winders, stringer notch depth and structural sizing are not included. Riser and tread limits are the base IRC values — your local code may be stricter. Always confirm with a builder or your building department before cutting.