Stair Rise & Run Calculator
Find the optimal rise and run for your stairs. Compare combinations, check IRC building code compliance, and use the comfort formula (2R+T) to find the most comfortable stair dimensions.
Your Configuration
Optimal Rise/Run Combinations
For a total rise of 108.00". Green rows meet IRC code and comfort formula.
| Risers | Rise/Step | Run/Step | 2R+T | Total Run | Code |
|---|---|---|---|---|---|
| 16 | 6 3/4" | 11" | 24.5"✓ | 165.00" (13.8 ft) | Pass |
| 15 | 7 1/4" | 10" | 24.4"✓ | 140.00" (11.7 ft) | Pass |
| 17 | 6 3/8" | 12" | 24.7"✓ | 192.00" (16.0 ft) | Pass |
| 17 | 6 3/8" | 11.5" | 24.2"✓ | 184.00" (15.3 ft) | Pass |
| 15 | 7 1/4" | 10.5" | 24.9"✓ | 147.00" (12.3 ft) | Pass |
| 16 | 6 3/4" | 10.5" | 24.0"✓ | 157.50" (13.1 ft) | Pass |
| 16 | 6 3/4" | 11.5" | 25.0"✓ | 172.50" (14.4 ft) | Pass |
| 18 | 6" | 12" | 24.0"✓ | 204.00" (17.0 ft) | Pass |
| 15 | 7 1/4" | 11" | 25.4"✓ | 154.00" (12.8 ft) | Pass |
| 14 | 7 3/4" | 10" | 25.4"✓ | 130.00" (10.8 ft) | Pass |
| 16 | 6 3/4" | 12" | 25.5"✓ | 180.00" (15.0 ft) | Pass |
| 14 | 7 3/4" | 9" | 24.4"✓ | 117.00" (9.8 ft) | Fail |
| 14 | 7 3/4" | 9.5" | 24.9"✓ | 123.50" (10.3 ft) | Fail |
| 15 | 7 1/4" | 9.5" | 23.9" | 133.00" (11.1 ft) | Fail |
| 17 | 6 3/8" | 11" | 23.7" | 176.00" (14.7 ft) | Pass |
| 16 | 6 3/4" | 10" | 23.5" | 150.00" (12.5 ft) | Pass |
| 18 | 6" | 11.5" | 23.5" | 195.50" (16.3 ft) | Pass |
| 15 | 7 1/4" | 9" | 23.4" | 126.00" (10.5 ft) | Fail |
| 13 | 8 1/4" | 9" | 25.6" | 108.00" (9.0 ft) | Fail |
| 19 | 5 5/8" | 12" | 23.4" | 216.00" (18.0 ft) | Pass |
IRC Code Reference
- R311.7.5.1 — Max riser height: 7-3/4" (197 mm)
- R311.7.5.2 — Min tread depth: 10" (254 mm)
- R311.7.5.1 — Max riser height variation: 3/8" between any two risers
- Comfort — 2R + T should equal 24–25" for comfortable stairs
How It Works
1. Choose your mode — enter either a specific number of steps or your desired rise per step. The calculator adjusts the other value automatically.
2. Enter total rise — measure floor-to-floor height in inches. Include finished flooring thickness on both levels.
3. Review combinations — the table shows every feasible riser count with multiple run options. Green rows meet both IRC code and the comfort formula.
4. Check code compliance — the calculator validates against IRC R311.7.5: max rise 7-3/4", min run 10", and max 3/8" variation between risers.
Use the comfort formula column to pick the combination that feels best. Values of 24–25" are ideal for typical residential stairs.
Frequently Asked Questions
What is the ideal rise and run for residential stairs?
The most comfortable residential stairs have a rise of 7" to 7-1/2" and a run (tread depth) of 10" to 11". This gives a comfort formula (2R+T) value between 24" and 25". The IRC allows a maximum rise of 7-3/4" and minimum run of 10".
How do I calculate the number of steps I need?
Divide your total rise (floor-to-floor height in inches) by your desired rise per step. For example, 108" total rise ÷ 7.5" per step = 14.4, so you'd use either 14 risers (7.71" each) or 15 risers (7.2" each). The calculator shows which option meets code.
What does the comfort formula 2R+T mean?
The comfort formula (2 × Riser height + Tread depth) predicts how comfortable stairs feel to walk. A result of 24" to 25" is ideal. Below 24" feels too flat/shallow. Above 25" feels too steep. For example: 2(7.25") + 10" = 24.5" — very comfortable.
Can I have different riser heights in one staircase?
IRC code (R311.7.5.1) allows a maximum variation of 3/8" between the tallest and shortest riser in a single flight. In practice, all risers should be exactly the same height. Uneven risers are a leading cause of stair falls. Always divide total rise evenly.