Stringer layout for a 90 inch rise
Calculate your stair design with a total rise of 90 inches. Ensure compliance with IRC riser limits of 7.75 inches for safe and comfortable stair construction.
Formula SSC-2026.1
IRC check pass
Risers / treads
12 / 11
Riser inside 4 to 7.75 in
Exact riser
7 1/2 in
190.5 mm
Total run
9 ft 7 1/2 in
2,934 mm
Stringer length
12 ft 2 7/16 in
Order 14 ft 2x12
Incline
37.93°
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 |
|---|---|---|---|---|---|---|
| 14 ft 2x12 | 12.83 ft cut | end cuts included | 3 boards | USD | $88.20 | Source Spec Material / Tool |
| Stringer delivery weight | 118 lb | — | 53 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.
| Total rise | Risers | Exact riser | Treads | Run | 2x12 stock | Check |
|---|---|---|---|---|---|---|
| 7 ft 6 in | 12 | 7 1/2 in | 11 | 9 ft 7 1/2 in | 14 ft | Pass |
| 8 ft 0 in | 13 | 7 3/8 in | 12 | 10 ft 6 in | 14 ft | Pass |
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: Stringer layout for a 90 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 stairs, it's crucial to adhere to the International Residential Code (IRC) guidelines. For a total rise of 90 inches, the maximum riser height is limited to 7.75 inches. This means you can have a maximum of 11 risers (90 inches / 7.75 inches = 11.61, rounded down to 11).
Note that headroom is not calculated in this context, but it's essential to ensure that your stairs provide adequate clearance for safe use.
Code reference
IRC Section R311.7.5
Field questions
- What is the maximum riser height allowed by the IRC?
- The maximum riser height allowed by the IRC is 7.75 inches.
- How many risers will I need for a total rise of 90 inches?
- For a total rise of 90 inches, you will need a maximum of 11 risers, given the 7.75 inch limit.
- Is headroom included in the stair design calculations?
- No, headroom is not calculated in this context, but it is important to ensure adequate clearance for safety.