About the stair calculator
Good stairs have identical risers and treads. Enter the total rise and your target riser height and tread depth to get the riser count, exact riser height, total run, and approximate stringer length.
How to use this calculator
- Measure the total rise from finished floor to finished floor.
- Set a target riser height and tread depth.
- Read the layout.
Worked examples
- 108 ÷ 7.5 = 14.4 → 15 risers
- 108 ÷ 15 = 7.2 in each
- 14 treads × 10.5 in = 147 in run
15 risers at 7.2 in, 12 ft 3 in of run.
Measurement guidance
Measure finished heights
Measure from finished floor to finished floor, including flooring thickness, so the top and bottom steps match the rest.
Frequently asked questions
Why one fewer tread than risers?
The top floor acts as the last step, so it isn’t counted as a tread.
What is a comfortable step?
A common guideline is 2 risers + 1 tread ≈ 24–25 inches (61–64 cm).