Enter the total rise from floor to floor and a target riser height, and get the riser count, actual riser height, tread depth, total run and approximate stringer length.
Code note: Building codes set maximum riser and minimum tread dimensions and vary by area. A common residential limit is a 7¾ in maximum riser and a 10 in minimum tread. Check local code before building; this is a planning calculation only.
The number of risers is the total rise divided by the target riser height, rounded to a whole number, and the actual riser height is the total rise divided by that count, so every riser is identical. Tread depth comes from the long-used comfort rule 2R + T, twice the riser height plus the tread depth, which should total roughly 24 to 26 inches (25 by default, editable within that range); the tread depth is the rule target minus twice the actual riser height. The number of treads is one less than the number of risers because the upper floor itself forms the last step, and total run is treads multiplied by tread depth. Approximate stringer length is the diagonal over the total run and total rise. Building codes set maximum riser and minimum tread dimensions and vary by area (a common residential limit is a 7 and three-quarter inch riser and a 10 inch tread), so check local code before building; this is a planning calculation, not a code approval.
What is the 2R + T rule for stairs? It is a comfort rule of thumb: twice the riser height plus the tread depth should total about 24 to 26 inches. Stairs that land in that range tend to match a natural stride. The calculator uses 25 inches by default and lets the target be edited between 24 and 26.
Do building codes limit riser height and tread depth? Yes. Building codes set maximum riser and minimum tread dimensions and vary by area; a common residential limit is a 7 and three-quarter inch maximum riser and a 10 inch minimum tread. Check local code before building, because this calculator is a planning tool and does not certify a design.
Why is there one fewer tread than risers? The top riser reaches the upper floor, and the floor itself is the walking surface for that step, so no tread board is needed for it. A flight with 14 risers has 13 treads.