Stair Calculator – Risers, Treads, and Rise/Run
Calculate number of stairs, riser height, and tread depth for any staircase.
About This Calculator
Calculate number of stairs, riser height, and tread depth for any staircase. Use the calculator above for instant results.
Worked Examples
- 108/7 = 15.4 → 15 risers
- Actual riser: 7.2in | Total run: 15 x 11in = 165in = 13.75ft
Answer: 15 risers / 13.75ft run
- 15 risers | Actual: 6.4in | Run: 15 x 11 = 165in
Answer: 15 risers
- 16 risers | Run: 16 x 11 = 176in = 14.67ft
Answer: 16 risers
Who Uses This Calculator?
Design and build code-compliant stairs.
Plan deck stair or interior stair addition.
Calculate staircase footprint.
Quick stair layout calculations.
Common Mistakes to Avoid
❌ Not accounting for finish flooring
If you haven't installed finish flooring yet, measure rough to rough and add floor thickness afterward.
❌ Rounding riser count incorrectly
Round to the nearest whole number of risers, then calculate actual riser height. Never have different-height risers in the same flight.
Frequently Asked Questions
Building code for stairs?
IRC code: max riser height 7-3/4 inches, min tread depth 10 inches, min width 36 inches, handrail 34-38 inches high.
Rise over run formula?
Comfortable stair formula: 2 × rise + run = 25-27 inches. 7in riser + 11in tread = 25 — ideal.
Number of risers vs treads?
Always one more riser than tread. 15 risers = 14 treads (the top floor is the last 'tread').