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Stair Calculator
Enter the total rise from floor to floor and the riser height you would like. The calculator picks the whole number of steps, evens out the riser, and gives the total run, the angle and the length of the slope. A 108 in rise gives 14 steps of about 7 11/16 in.
Updated · Sources re-checked by
14 steps (risers)
| Exact riser height | 7 11/16 in |
| Treads | 13 × 10 in |
| Total run | 130 in (10 ft 10 in) |
| Stair angle | 37.6 degrees |
| Slope length | 169 in (14 ft 1 in) |
| 2 × riser + tread | 25 7/16 in |
- Meets: riser at most 7 3/4 in (US residential)
- Meets: tread at least 10 in (US residential)
- Check: 2 × riser + tread between 24 and 25 in
Local building codes decide the final limits. You can type 108, 108.5, 9 ft or 4 1/2. Nothing you type is saved or sent anywhere.
How the stair calculator works
Number of risers = total rise ÷ the riser height you want, rounded to a whole number. Actual riser = total rise ÷ number of risers, so every step is the same. Treads = risers − 1, because the top floor is the last step. Total run = treads × tread depth. Angle = arctan(riser ÷ tread). Slope length = √(total rise² + total run²). Comfort check: 2 × riser + tread, which is about 24 to 25 in on stairs that feel natural. Code check: riser no more than 7.75 in and tread at least 10 in (US residential, IRC R311.7).
| Floor to floor | Steps | Riser | Total run |
|---|---|---|---|
| 8 ft (96 in) | 13 | 7 3/8 in | 10 ft 0 in |
| 9 ft (108 in) | 14 | 7 11/16 in | 10 ft 10 in |
| 10 ft (120 in) | 16 | 7 1/2 in | 12 ft 6 in |
| 12 ft (144 in) | 19 | 7 9/16 in | 15 ft 0 in |
| Part | Limit |
|---|---|
| Riser height | 7.75 in at most |
| Tread depth | 10 in at least |
| Riser difference in one flight | 3/8 in at most between the tallest and shortest |
| Headroom | 6 ft 8 in at least |
| Stair width | 36 in at least |
Worked example: 108 in from floor to floor
- Steps: 108 ÷ 7.5 = 14.4, so 14 risers.
- Actual riser: 108 ÷ 14 = 7.714 in, about 7 11/16 in.
- Treads: 14 − 1 = 13. Total run: 13 × 10 = 130 in, 10 ft 10 in.
- Angle: arctan(7.714 ÷ 10) = 37.6 degrees.
- Slope length: √(108² + 130²) = 169 in, 14 ft 1 in. Comfort: 2 × 7.71 + 10 = 25.4 in, a little steep for comfort. Try an 11 in tread.
Common questions
How do I calculate the number of steps in a staircase?
Measure the total rise from the finished floor below to the finished floor above, and divide by the riser height you want, about 7 to 7 3/4 in. Round to a whole number, then divide the rise by that whole number to get the exact riser.
How many treads are there compared with risers?
One fewer. The top floor works as the last tread, so a stair with 14 risers has 13 treads. Total run is the number of treads times the tread depth.
What is the maximum riser height and minimum tread depth?
For US homes the model code allows a riser up to 7 3/4 in and requires a tread of at least 10 in. Your local building department makes the final call, so check before you build.
What does 2 × riser + tread mean?
It is an old comfort rule: two risers plus one tread should come to about 24 to 25 in. Steps that fall outside it can still meet code, but they feel steep or too shallow.
What angle should stairs be?
Most home stairs fall between about 30 and 37 degrees. A 7 in riser with an 11 in tread is about 32 degrees, and 7 3/4 in with 10 in is about 38.
Do I measure rise to the subfloor or the finished floor?
Use the finished floors at the top and bottom. If the flooring thickness differs, adjust the first and last riser so every finished step ends up the same height.
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Sources
- International Residential Code, chapter 3 (R311.7 stairways): riser, tread and headroom limits. Local codes can differ (checked October 28, 2026)
- OSHA 1926.1052: stairways on construction sites (riser and tread uniformity) (checked October 28, 2026)
- Stairs: rise, run and the 2 x riser + tread comfort rule (checked October 28, 2026)
This calculator is an estimate for planning. Stair rules vary by place and by the kind of building, so confirm the limits with your local building department before you cut any wood.