Stairs Calculator
Riser height, tread depth, and stringer length for a staircase.
Total run: 154.0 in (12.8 ft)
Stair angle: 33.2°
Stringer length: 188.1 in
2× riser + tread: 25.40 in (outside 24–25 comfort range)
IRC compliance: yes (riser 4–7.75, tread ≥10)
Alt: 14 steps
Riser 7.71 in · run 11.9 ft · angle 35.0°
Residential code (IRC) caps risers at 7¾ in and requires treads of at least 10 in. The 2R + T comfort rule wants the result between 24 and 25 inches. All risers and treads must be uniform within ⅜ in.
About
Enter total floor-to-floor rise plus your target riser height and tread depth. The tool calculates the number of steps that keep risers under the IRC 7¾ in cap, total run, stair angle, and stringer length. Also flags the 2R+T comfort rule.
How to use
- Enter total rise (floor to floor).
- Set your target riser height and tread.
- Read steps, angle, and stringer length.
FAQ
What's the comfort rule?+
2 × riser + tread should land between 24 and 25 inches. Below 24 feels cramped, above 25 feels stretched.
Why two suggestions sometimes?+
When the math lands between two step counts, the tool shows both so you can pick the riser height that feels right.