Stair layout for a 120 inch rise
Calculate your stair design with a total rise of 120 inches, adhering to IRC guidelines of 7.75 inch risers and 10 inch treads. Ensure safety and compliance in your construction project.
Formula SSC-2026.1
IRC check pass
Risers / treads
16 / 15
Riser inside 4 to 7.75 in
Exact riser
7 1/2 in
190.5 mm
Total run
13 ft 1 1/2 in
4,001 mm
Stringer length
16 ft 6 in
Order 18 ft 2x12
Incline
37.30°
Square 7 1/2 in rise · 10 1/2 in run
Stringers @ 16 in
3
Throat 5.15 in on a 2x12
Rise, run, and the incline are scaled from the live riser and tread. Framing-square gauges match the exact riser and the tread depth.
| Item | Net | Waste | Order | Unit price | Line total | Source Spec Material / Tool |
|---|---|---|---|---|---|---|
| 18 ft 2x12 | 17.13 ft cut | end cuts included | 3 boards | USD | $113.40 | Source Spec Material / Tool |
| Stringer delivery weight | 151 lb | — | 69 kg | 2.8 lb/ft planning weight | — | Source Spec Material / Tool |
Source links open a product search on the Amazon storefront for the selected currency. SiteSpecCalc may earn a commission. The link does not change the quantities above.
| Target | Risers | Exact riser | Run | Angle | Check |
|---|---|---|---|---|---|
| 7 in | 17 | 7 1/16 in | 14 ft 0 in | 35.5° | Pass |
| 7 1/2 in | 16 | 7 1/2 in | 13 ft 1 1/2 in | 37.3° | Pass |
| 7 3/4 in | 15 | 8 in | 12 ft 3 in | 39.2° | Warning |
Show the deterministic formula
Risers = round(total rise ÷ target rise). Exact riser = total rise ÷ risers, reported to the nearest 1/16 in and in millimeters. Treads = risers − 1. Total run = treads × tread depth.
Diagonal = hypotenuse of stringer rise and total run. A dropped header uses total rise minus landing thickness. Stock is the next 8, 10, 12, 14, 16, 18, 20, or 24 ft board.
Stringers = floor(width ÷ 16) + 1, with a minimum of 2. Throat ≈ 11.25 − (riser × tread) ÷ hypotenuse.
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Project: Stair layout for a 120 inch rise
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This sheet is an estimate for ordering and layout discussion. It is not a sealed design. Confirm the quantities with a licensed local professional and the authority having jurisdiction before you buy or build.
Engineering notes
When designing a stair with a total rise of 120 inches, you must adhere to the International Residential Code (IRC) guidelines, which stipulate a maximum riser height of 7.75 inches and a minimum tread depth of 10 inches. This ensures safety and accessibility in residential staircases.
It's important to note that headroom is not calculated in this design, but it should still be considered to meet safety standards.
Code reference
IRC guidelines for stair design
Field questions
- What is the maximum riser height allowed by IRC?
- The maximum riser height allowed by the IRC is 7.75 inches.
- What is the minimum tread depth required for stairs?
- The minimum tread depth required for stairs according to the IRC is 10 inches.
- Is headroom calculated in stair design?
- No, headroom is not calculated in the stair design, but it should be considered for safety.
- How do I calculate the number of risers for a 120 inch total rise?
- To calculate the number of risers, divide the total rise (120 inches) by the maximum riser height (7.75 inches). This gives you approximately 15.48, so you would round up to 16 risers.