Stair calculator
Work out how many steps you need, the exact riser and tread sizes, the total run and the stringer length.
About this calculator
Measure the total rise from the finished floor below to the finished floor above, then choose the riser height you want. The calculator rounds to a whole number of steps and recalculates the exact riser height.
It also gives the total run, the stringer length for cutting, the angle, and a comfort check.
Measurements and terms explained
- Total rise
- The vertical height from the lower finished floor to the upper finished floor.
- Riser
- The vertical part of one step. All risers should be equal.
- Tread depth
- The flat part you stand on, measured front to back.
- Total run
- The horizontal distance the staircase covers, equal to the number of treads times the tread depth.
- Stringer
- The sloped board that carries the treads. Its length is the diagonal of the rise and run.
- 2R + T rule
- Twice the riser plus the tread should be 24 to 25.5 inches (61 to 65 cm) for a comfortable stride.
Common questions
What is a comfortable riser and tread?
Many homes use risers of about 7 to 7.75 inches (18 to 19.5 cm) and treads of at least 10 inches (25 cm). Local rules set the limits.
Why one fewer tread than risers?
The top floor acts as the last step, so there is always one more riser than tread.
More free calculators
Concrete calculator
Volume and bags of concrete for a slab.
Square footage calculator
Area of a room, plot or shape in any unit.
Roofing calculator
Roof area, squares and shingle bundles from pitch.
Tile calculator
How many tiles and boxes you need for a floor or wall.
Mulch calculator
Cubic yards, metres and bags of mulch for a bed.
Gravel calculator
Volume and weight of gravel, stone or sand.