Stair Calculator
Calculate stair dimensions, rise, run, and building code compliance
Vertical distance between floors
Available horizontal space
Number of Steps
12 treads
Actual Rise
Code compliant
Actual Run
Code compliant
Stair Angle
Good angle
Not Code Compliant
Construction Details
Advanced Settings
Material thickness
Tread overhang
Minimum clearance
2x12 = 11.25"
Quick Reference
Code Requirements
Design Guidelines
How it works
A stair calculator works out the number of steps and their dimensions from the total height to climb. Divide the total rise by a comfortable step height (~7 inches) to get the number of risers, then check the run against building-code limits.
Stair layout
Number of risers = total rise ÷ target riser height Each riser = total rise ÷ number of risers
- total rise
- floor-to-floor vertical height
- riser height
- comfortable ~7 in (code-limited)
- run/tread
- horizontal depth of each step (~10–11 in)
Worked example
- Total rise = 112 inches
- Risers = 112 ÷ 7 = 16
- Each riser = 112 ÷ 16 = 7 in exactly
16 risers (15 treads) at 7 inches each.
Good to know
- Codes cap riser height (often ~7.75 in max) and set a minimum tread depth (~10 in) — check local rules.
- Keep every riser the same height; uneven steps are a trip hazard and usually fail inspection.
- The “2R + T ≈ 25 in” rule of thumb makes stairs feel comfortable.
Related Calculators
Frequently Asked Questions
What are standard stair rise and run dimensions?
Under the IRC residential code, risers can be at most 7¾ inches and treads at least 10 inches deep. Commercial stairs under IBC are gentler: maximum 7-inch risers and minimum 11-inch treads. Always confirm local amendments.
How do I calculate the number of steps?
Divide the total rise (floor to floor) by your target riser height and round to a whole number, then divide back to get the exact riser. A 108-inch rise with ~7.5-inch risers gives 14 steps of 7.71 inches each.
Why must all risers be the same height?
Uneven steps cause trips and falls, so codes typically limit riser variation to 3/8 inch across the flight. The calculator distributes the total rise evenly to keep every step identical.
What makes a staircase comfortable to climb?
The classic rule of thumb: 2 x rise + run should total about 24-25 inches (alternatively, rise + run near 17-18 inches). A 7-inch rise with an 11-inch run hits the sweet spot.
What other code requirements apply to stairs?
Plan for at least 6'8" of headroom along the entire flight, handrails set 34-38 inches above the tread nosings, and minimum stair width (36 inches for residential). Landings are required at the top and bottom.