Stair Rise & Run Calculator
Calculate code-compliant stair dimensions from total floor-to-floor height.
Stair Dimensions by Total Rise
Using 7.5" target rise and 10.5" run
| Total Rise | Risers | Actual Rise | Total Run | Stringer | Angle |
|---|---|---|---|---|---|
| 36" (3') | 5 | 7.20" | 42" | 55.3" | 40.6° |
| 72" (6') | 10 | 7.20" | 94.5" | 118.8" | 37.3° |
| 96" (8') | 13 | 7.38" | 126" | 158.4" | 37.3° |
| 108" (9') | 14 | 7.71" | 136.5" | 174.1" | 38.4° |
| 118" (9'10") | 16 | 7.38" | 157.5" | 196.9" | 36.8° |
| 132" (11') | 18 | 7.33" | 178.5" | 222.0" | 36.5° |
How We Calculate This
This stair rise & run calculator uses established formulas and industry-standard data to provide accurate estimates.
- Enter your specific values into the calculator fields above
- Our algorithm applies the relevant formulas using your inputs
- Results are calculated instantly in your browser — nothing is sent to a server
- Review the detailed breakdown to understand how each factor affects your result
These calculations are estimates based on standard formulas. For critical decisions, always consult a qualified professional.
How to Convert Oven Recipes to Air Fryer
This calculator determines code-compliant stair dimensions by dividing total floor-to-floor height by desired riser height, then checking against IRC building code requirements.
The basic rule:
- Number of risers = total rise ÷ desired riser height (rounded to nearest whole number)
- Actual riser height = total rise ÷ number of risers
- Number of treads = number of risers − 1 (the floor counts as the last tread)
- Total run = number of treads × tread depth
- Stringer length = √(total rise² + total run²) — the hypotenuse
- Comfort rule: rise + run should be between 17" and 18" for optimal comfort
IRC 2021 code limits: max riser height 7.75", min tread depth 10", min width 36" clear, min headroom 6'8". All risers must be uniform within 3/8" of each other. Local codes may be stricter — always verify with your building department.
When Would You Use This Calculator?
This stair rise & run calculator is designed for anyone who needs quick, reliable estimates without complex spreadsheets or professional consultations.
- When you need a quick estimate before committing to a purchase or project
- When comparing different options or scenarios side by side
- When planning a budget and need to understand potential costs
- When you want to verify a quote or estimate you've received from a professional
- When teaching or learning about the concepts behind these calculations
Frequently Asked Questions
What is the ideal stair rise and run?
The ideal residential stair has a 7" to 7.5" rise and 10" to 11" run. The classic comfort rule is that rise + run should equal 17" to 18". A 7" rise with 11" run (total 18") is widely considered the most comfortable combination.
What is the maximum riser height allowed by code?
The IRC (International Residential Code) allows a maximum riser height of 7.75" (7-3/4"). The minimum tread depth is 10". Some states and municipalities have stricter requirements — California, for example, limits risers to 7.5" in some cases.
How do I calculate stringer length?
Stringer length is the hypotenuse of the stair triangle: √(total rise² + total run²). For example, with a 108" total rise and 147" total run, the stringer length is √(108² + 147²) = √(11,664 + 21,609) = √33,273 ≈ 182.4" or about 15.2 feet.
What angle should stairs be?
Residential stairs should be between 30° and 37° for comfortable use. The ideal angle is about 33-34°. Steeper than 37° feels unsafe; shallower than 30° wastes floor space. Code-compliant stairs (7.75" rise, 10" run) result in about 37.8°.
How many steps for a 9-foot ceiling?
A 9-foot ceiling typically requires 14-15 risers. With a 9' ceiling, total rise is about 108-110" (including floor/ceiling thickness). At 7.5" per riser, that's 14-15 risers with 13-14 treads, requiring about 12 feet of horizontal run.
Do all risers need to be the same height?
Yes, building code requires all risers to be uniform within 3/8" of each other. The largest and smallest riser in a flight cannot differ by more than 3/8". This is a safety requirement — uneven risers are a leading cause of stair falls.