Stair Stringer Layout Calculator
IRC check pass
Risers / treads
10 / 9
Riser inside 4 to 7.75 in
Exact riser
7 3/16 in
182.9 mm
Total run
7 ft 10 1/2 in
2,400 mm
Stringer length
9 ft 10 13/16 in
Order 12 ft 2x12
Incline
37.30°
Square 7 3/16 in rise · 10 1/2 in run
Stringers @ 16 in
3
Throat 5.31 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 |
|---|---|---|---|---|---|---|
| 12 ft 2x12 | 10.50 ft cut | end cuts included | 3 boards | USD | $75.60 | Source Spec Material / Tool |
| Stringer delivery weight | 101 lb | — | 46 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 | 10 | 7 3/16 in | 7 ft 10 1/2 in | 37.3° | Pass |
| 7 1/4 in | 10 | 7 3/16 in | 7 ft 10 1/2 in | 37.3° | Pass |
| 7 1/2 in | 10 | 7 3/16 in | 7 ft 10 1/2 in | 37.3° | Pass |
| 7 3/4 in | 9 | 8 in | 7 ft 0 in | 40.6° | 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 Stringer Layout Calculator
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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.