Stringer layout for a 48 inch rise
Use our stair design calculator to determine total rise and ensure compliance with IRC riser limits of 7.75 inches. Headroom calculations not included.
Formula SSC-2026.1
IRC check warning
Risers / treads
6 / 5
Try 7 risers
Exact riser
8 in
203.2 mm
Total run
4 ft 4 1/2 in
1,334 mm
Stringer length
5 ft 11 1/8 in
Order 8 ft 2x12
Incline
42.44°
Square 8 in rise · 10 1/2 in run
Stringers @ 16 in
3
Throat 4.89 in on a 2x12
- Riser is taller than the 7.75 in IRC maximum.
- Estimated 2x12 throat is under 5 in. Confirm with the local inspector.
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 |
|---|---|---|---|---|---|---|
| 8 ft 2x12 | 6.59 ft cut | end cuts included | 3 boards | USD | $50.40 | Source Spec Material / Tool |
| Stringer delivery weight | 67 lb | — | 30 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 |
|---|---|---|---|---|---|---|
| 4 ft 0 in | 6 | 8 in | 5 | 4 ft 4 1/2 in | 8 ft | Warning |
| 4 ft 6 in | 7 | 7 11/16 in | 6 | 5 ft 3 in | 8 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.
Contractor sign-off
Project: Stringer layout for a 48 inch rise
Prepared by
Date
Verified by (PE / electrician / inspector)
License number
Signature
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 48 inches, the maximum riser height allowed is 7.75 inches. This means you can have a maximum of 6 risers (48 ÷ 7.75 = 6.19, rounded down to 6).
Note that headroom calculations are not included in this assessment and should be considered separately to ensure safety and comfort.
Code reference
IRC Section R311.7.5
Field questions
- What is the maximum riser height according to the IRC?
- The maximum riser height allowed by the IRC is 7.75 inches.
- How do I calculate the number of risers for a total rise of 48 inches?
- To calculate the number of risers, divide the total rise by the maximum riser height. For a total rise of 48 inches, you would divide 48 by 7.75, which gives approximately 6 risers.
- Is headroom included in the stair design calculations?
- No, headroom calculations are not included in this assessment and should be evaluated separately.