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Stair Rise & Run Calculator
Enter your total rise and preferred riser height — get number of steps, tread depth, stringer length, and IRC code compliance instantly.
Step 1 — Enter Your Measurements
- Order stringer material 10–15% longer than calculated stringer length to allow for layout cuts
- All risers must be within 3/8" of each other — inconsistent risers cause trips and fail inspection
- Minimum headroom is 6'–8" (80") measured vertically from tread nosing to ceiling
- Handrail required on stairs with 4 or more risers — graspable rail 34"–38" above nosing
- Always verify with your local building department — some jurisdictions have stricter requirements
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Stair Code Quick Reference (IRC R311.7)
International Residential Code minimum requirements for residential stair construction. Always verify with your local building department — some jurisdictions adopt stricter standards.
| Requirement | IRC Minimum/Maximum | Notes |
|---|---|---|
| Max riser height | 7-3/4" (197mm) | Measured vertically between tread nosings |
| Min riser height | 4" (102mm) | Open risers permitted if opening < 4" |
| Min tread depth | 10" (254mm) | Measured horizontally, nosing to nosing |
| Max riser variation | 3/8" (9.5mm) | Between largest and smallest riser in same stair |
| Min stair width | 36" (914mm) | Clear width above handrail height |
| Min headroom | 6'-8" (2032mm) | Vertical clearance from nosing to ceiling |
| Handrail height | 34"–38" (864–965mm) | Measured above tread nosing |
| Handrail required | 4 or more risers | Graspable rail on at least one side |
| Nosing projection | 3/4"–1-1/4" | Uniform projection on all treads |
| Landing size | Min 36" x 36" | At top and bottom of each stair run |
Common Stair Configurations
Pre-calculated stair specs for common floor-to-floor heights. All configurations are IRC compliant with 7" risers and 10.5" treads.
| Floor-to-Floor Height | Risers | Actual Riser | Treads | Total Run | Stringer |
|---|---|---|---|---|---|
| 84" (7 ft) | 12 | 7" | 11 | 115.5" | 134" |
| 96" (8 ft) | 14 | 6-7/8" | 13 | 136.5" | 158" |
| 108" (9 ft) | 15 | 7-1/4" | 14 | 147" | 170" |
| 120" (10 ft) | 17 | 7-1/16" | 16 | 168" | 195" |
| 132" (11 ft) | 19 | 6-15/16" | 18 | 189" | 219" |
| 144" (12 ft) | 21 | 6-7/8" | 20 | 210" | 243" |
Stringer Length by Rise and Run
Quick stringer length reference. Add 10–15% for layout waste. Values are for the cut stringer length (hypotenuse of the total rise and total run triangle).
| Total Rise | Total Run | Stringer Length | Order Length |
|---|---|---|---|
| 84" | 110" | 138" | 12 ft |
| 96" | 126" | 158" | 14 ft |
| 108" | 140" | 177" | 16 ft |
| 120" | 157" | 197" | 18 ft |
| 132" | 173" | 218" | 20 ft |
| 144" | 189" | 238" | 22 ft |
Always verify stair specifications with your local building department. IRC requirements shown — local codes may differ.