Stair Calculator
Plan a staircase. Enter the height from floor to floor, the maximum riser height, and the tread depth to see how many steps you need, the exact riser height, the total run, and the stringer length.
Number of steps (risers)
14
Check the highlighted fields to see your result.
- Each riser
- 7.71 in
- Treads
- 13
- Total run
- 130 in
- Stringer length
- 169.01 in
- Angle
- 37.6°
- 2 risers + tread
- 25.43 in (comfortable)
Check your local building code before you build. Codes set limits for risers, treads, headroom, and handrails.
Results are estimates for information only and do not constitute financial, medical, or legal advice.
How it works
The calculator divides the total rise by your maximum riser height and rounds up to get the number of steps, so no step is taller than you allow. Then it splits the height evenly so all risers are the same, which is safer and usually required by code.
The formulas
- Risers = total rise ÷ max riser, rounded up
- Riser height = total rise ÷ risers
- Treads = risers − 1 · Total run = treads × tread depth
- Stringer = √(total rise² + total run²)
Worked example
The floor-to-floor height is 108 inches, with risers up to 7¾ in and 10-inch treads.
- 108 ÷ 7.75 = 13.9, rounded up to 14 risers.
- Each riser: 108 ÷ 14 ≈ 7.71 in.
- 13 treads × 10 in = 130 in of total run, and a stringer of about 169 in.
Frequently asked questions
What's the difference between a riser and a tread?
The riser is the vertical height of each step, and the tread is the horizontal part you step on. A staircase always has one more riser than treads, because the last step up lands on the upper floor.
What does the US building code require?
The International Residential Code (IRC), used in most US states, allows risers up to 7¾ inches and requires treads of at least 10 inches, with all risers in a flight within ⅜ inch of each other. Local codes can be stricter, so check with your building department.
What is the 2R + T rule?
A comfort rule: twice the riser height plus the tread depth should be about 24 to 25 inches (60 to 65 cm), close to the length of a normal step. Stairs outside that range feel too steep or too shallow.