Header size calculator: what size header do I need?
2-2 × 10 header
spans up to 6 ft 10 in at 24 ft wide, 30 psf snow · 2 jack studs each end · for a 6 ft opening
Run your own numbers
Enter it the way you measured it: 4.5, 4 1/2,
3/8 or 10' 6".
2-2 × 10 header
spans up to 6 ft 10 in at 24 ft wide, 30 psf snow · 2 jack studs each end
Source: IRC 2021 Tables R602.7(1) and R602.7(2), header spans, in the 2021 Seattle Residential Code chapter 6, read October 26, 2026. Data sheet (PDF)
A 6 ft opening in an exterior wall carrying roof and ceiling, on a 24 ft wide house at 30 psf ground snow, takes a 2-2 × 10 header: IRC 2021 Table R602.7(1) allows 6 ft 10 in, with 2 jack studs each end.
A worked example
A 3 ft 2 in doorway in an interior bearing wall under two floors of a 30 ft wide house needs a 2-2 × 8 header. Table R602.7(2) gives a 2-2 × 8 3-8 at 24 ft and 3-1 at 36 ft; halfway, at 30 ft, that is 3 ft 4 1/2 in, enough for 3 ft 2 in, with 2 jack studs each end. A 2-2 × 6 reaches only 2 ft 8 in there.
What size header for a 6 ft or 8 ft opening?
In an exterior wall under roof and ceiling only, at 30 psf ground snow: on a 24 ft wide house a 6 ft opening takes a 2-2 × 10 (6 ft 10 in) and an 8 ft one a 2-2 × 12 (8 ft 1 in); on a 36 ft wide house the 6 ft opening already needs a 2-2 × 12 and the 8 ft one a 3-2 × 12.
How many jack studs does a header need?
The NJ column of the table gives it for each end: from 1 to 4 depending on size, load and width. Where it says 1, the IRC lets an approved framing anchor on the full-height stud take the place of the jack stud.
What if cripple studs sit on the header?
Then nothing braces its top, and IRC note f cuts the span of 2 × 8, 2 × 10 and 2 × 12 headers to 70%. The 6 ft opening above goes from a 2-2 × 10 to a 3-2 × 10.
What else it is called
Also searched as a header size calculator for doors, garage door header size or window header size; the code calls them headers and girders. Building width is measured perpendicular to the ridge, wall to wall.
The full IRC table
| Supporting · size | 30 psf, 12 ft wide | 30 psf, 24 ft wide | 30 psf, 36 ft wide | 50 psf, 12 ft wide | 50 psf, 24 ft wide | 50 psf, 36 ft wide | 70 psf, 12 ft wide | 70 psf, 24 ft wide | 70 psf, 36 ft wide |
|---|---|---|---|---|---|---|---|---|---|
| Roof and ceiling · 1-2 × 6 | 4-0 (1) | 3-1 (2) | 2-7 (2) | 3-5 (1) | 2-8 (2) | 2-3 (2) | 3-0 (2) | 2-4 (2) | 2-0 (2) |
| Roof and ceiling · 1-2 × 8 | 5-1 (2) | 3-11 (2) | 3-3 (2) | 4-4 (2) | 3-4 (2) | 2-10 (2) | 3-10 (2) | 3-0 (2) | 2-6 (3) |
| Roof and ceiling · 1-2 × 10 | 6-0 (2) | 4-8 (2) | 3-11 (2) | 5-2 (2) | 4-0 (2) | 3-4 (3) | 4-7 (2) | 3-6 (3) | 3-0 (3) |
| Roof and ceiling · 1-2 × 12 | 7-1 (2) | 5-5 (2) | 4-7 (3) | 6-1 (2) | 4-8 (3) | 3-11 (3) | 5-5 (2) | 4-2 (3) | 3-6 (3) |
| Roof and ceiling · 2-2 × 4 | 4-0 (1) | 3-1 (1) | 2-7 (1) | 3-5 (1) | 2-7 (1) | 2-2 (1) | 3-0 (1) | 2-4 (1) | 2-0 (1) |
| Roof and ceiling · 2-2 × 6 | 6-0 (1) | 4-7 (1) | 3-10 (1) | 5-1 (1) | 3-11 (1) | 3-3 (2) | 4-6 (1) | 3-6 (2) | 2-11 (2) |
| Roof and ceiling · 2-2 × 8 | 7-7 (1) | 5-9 (1) | 4-10 (2) | 6-5 (1) | 5-0 (2) | 4-2 (2) | 5-9 (1) | 4-5 (2) | 3-9 (2) |
| Roof and ceiling · 2-2 × 10 | 9-0 (1) | 6-10 (2) | 5-9 (2) | 7-8 (2) | 5-11 (2) | 4-11 (2) | 6-9 (2) | 5-3 (2) | 4-5 (2) |
| Roof and ceiling · 2-2 × 12 | 10-7 (2) | 8-1 (2) | 6-10 (2) | 9-0 (2) | 6-11 (2) | 5-10 (2) | 8-0 (2) | 6-2 (2) | 5-2 (3) |
| Roof and ceiling · 3-2 × 8 | 9-5 (1) | 7-3 (1) | 6-1 (1) | 8-1 (1) | 6-3 (1) | 5-3 (2) | 7-2 (1) | 5-6 (2) | 4-8 (2) |
| Roof and ceiling · 3-2 × 10 | 11-3 (1) | 8-7 (1) | 7-3 (2) | 9-7 (1) | 7-4 (2) | 6-2 (2) | 8-6 (1) | 6-7 (2) | 5-6 (2) |
| Roof and ceiling · 3-2 × 12 | 13-2 (1) | 10-1 (2) | 8-6 (2) | 11-3 (2) | 8-8 (2) | 7-4 (2) | 10-0 (2) | 7-9 (2) | 6-6 (2) |
| Roof and ceiling · 4-2 × 8 | 10-11 (1) | 8-4 (1) | 7-0 (1) | 9-4 (1) | 7-2 (1) | 6-0 (1) | 8-3 (1) | 6-4 (1) | 5-4 (2) |
| Roof and ceiling · 4-2 × 10 | 12-11 (1) | 9-11 (1) | 8-4 (1) | 11-1 (1) | 8-6 (1) | 7-2 (2) | 9-10 (1) | 7-7 (2) | 6-4 (2) |
| Roof and ceiling · 4-2 × 12 | 15-3 (1) | 11-8 (1) | 9-10 (2) | 13-0 (1) | 10-0 (2) | 8-5 (2) | 11-7 (1) | 8-11 (2) | 7-6 (2) |
| Roof, ceiling, one center-bearing floor · 1-2 × 6 | 3-3 (1) | 2-7 (2) | 2-2 (2) | 3-0 (2) | 2-4 (2) | 2-0 (2) | 2-9 (2) | 2-2 (2) | 1-10 (2) |
| Roof, ceiling, one center-bearing floor · 1-2 × 8 | 4-1 (2) | 3-3 (2) | 2-9 (2) | 3-9 (2) | 3-0 (2) | 2-6 (3) | 3-6 (2) | 2-9 (2) | 2-4 (3) |
| Roof, ceiling, one center-bearing floor · 1-2 × 10 | 4-11 (2) | 3-10 (2) | 3-3 (3) | 4-6 (2) | 3-6 (3) | 3-0 (3) | 4-1 (2) | 3-3 (3) | 2-9 (3) |
| Roof, ceiling, one center-bearing floor · 1-2 × 12 | 5-9 (2) | 4-6 (3) | 3-10 (3) | 5-3 (2) | 4-2 (3) | 3-6 (3) | 4-10 (3) | 3-10 (3) | 3-3 (4) |
| Roof, ceiling, one center-bearing floor · 2-2 × 4 | 3-3 (1) | 2-6 (1) | 2-2 (1) | 3-0 (1) | 2-4 (1) | 2-0 (1) | 2-8 (1) | 2-2 (1) | 1-10 (1) |
| Roof, ceiling, one center-bearing floor · 2-2 × 6 | 4-10 (1) | 3-9 (1) | 3-3 (2) | 4-5 (1) | 3-6 (2) | 3-0 (2) | 4-1 (1) | 3-3 (2) | 2-9 (2) |
| Roof, ceiling, one center-bearing floor · 2-2 × 8 | 6-1 (1) | 4-10 (2) | 4-1 (2) | 5-7 (2) | 4-5 (2) | 3-9 (2) | 5-2 (2) | 4-1 (2) | 3-6 (2) |
| Roof, ceiling, one center-bearing floor · 2-2 × 10 | 7-3 (2) | 5-8 (2) | 4-10 (2) | 6-8 (2) | 5-3 (2) | 4-5 (2) | 6-1 (2) | 4-10 (2) | 4-1 (2) |
| Roof, ceiling, one center-bearing floor · 2-2 × 12 | 8-6 (2) | 6-8 (2) | 5-8 (2) | 7-10 (2) | 6-2 (2) | 5-3 (3) | 7-2 (2) | 5-8 (2) | 4-10 (3) |
| Roof, ceiling, one center-bearing floor · 3-2 × 8 | 7-8 (1) | 6-0 (1) | 5-1 (2) | 7-0 (1) | 5-6 (2) | 4-8 (2) | 6-5 (1) | 5-1 (2) | 4-4 (2) |
| Roof, ceiling, one center-bearing floor · 3-2 × 10 | 9-1 (1) | 7-2 (2) | 6-1 (2) | 8-4 (1) | 6-7 (2) | 5-7 (2) | 7-8 (2) | 6-1 (2) | 5-2 (2) |
| Roof, ceiling, one center-bearing floor · 3-2 × 12 | 10-8 (2) | 8-5 (2) | 7-2 (2) | 9-10 (2) | 7-8 (2) | 6-7 (2) | 9-0 (2) | 7-1 (2) | 6-1 (2) |
| Roof, ceiling, one center-bearing floor · 4-2 × 8 | 8-10 (1) | 6-11 (1) | 5-11 (1) | 8-1 (1) | 6-4 (1) | 5-5 (2) | 7-5 (1) | 5-11 (1) | 5-0 (2) |
| Roof, ceiling, one center-bearing floor · 4-2 × 10 | 10-6 (1) | 8-3 (2) | 7-0 (2) | 9-8 (1) | 7-7 (2) | 6-5 (2) | 8-10 (1) | 7-0 (2) | 6-0 (2) |
| Roof, ceiling, one center-bearing floor · 4-2 × 12 | 12-4 (1) | 9-8 (2) | 8-3 (2) | 11-4 (2) | 8-11 (2) | 7-7 (2) | 10-4 (2) | 8-3 (2) | 7-0 (2) |
| Roof, ceiling, one clear-span floor · 1-2 × 6 | 2-11 (2) | 2-3 (2) | 1-11 (2) | 2-9 (2) | 2-1 (2) | 1-9 (2) | 2-7 (2) | 2-0 (2) | 1-8 (2) |
| Roof, ceiling, one clear-span floor · 1-2 × 8 | 3-9 (2) | 2-10 (2) | 2-5 (3) | 3-6 (2) | 2-8 (2) | 2-3 (3) | 3-3 (2) | 2-6 (3) | 2-2 (3) |
| Roof, ceiling, one clear-span floor · 1-2 × 10 | 4-5 (2) | 3-5 (3) | 2-10 (3) | 4-2 (2) | 3-2 (3) | 2-8 (3) | 3-11 (2) | 3-0 (3) | 2-6 (3) |
| Roof, ceiling, one clear-span floor · 1-2 × 12 | 5-2 (2) | 4-0 (3) | 3-4 (3) | 4-10 (3) | 3-9 (3) | 3-2 (4) | 4-7 (3) | 3-6 (3) | 3-0 (4) |
| Roof, ceiling, one clear-span floor · 2-2 × 4 | 2-11 (1) | 2-3 (1) | 1-10 (1) | 2-9 (1) | 2-1 (1) | 1-9 (1) | 2-7 (1) | 2-0 (1) | 1-8 (1) |
| Roof, ceiling, one clear-span floor · 2-2 × 6 | 4-4 (1) | 3-4 (2) | 2-10 (2) | 4-1 (1) | 3-2 (2) | 2-8 (2) | 3-10 (1) | 3-0 (2) | 2-6 (2) |
| Roof, ceiling, one clear-span floor · 2-2 × 8 | 5-6 (2) | 4-3 (2) | 3-7 (2) | 5-2 (2) | 4-0 (2) | 3-4 (2) | 4-10 (2) | 3-9 (2) | 3-2 (2) |
| Roof, ceiling, one clear-span floor · 2-2 × 10 | 6-7 (2) | 5-0 (2) | 4-2 (2) | 6-1 (2) | 4-9 (2) | 4-0 (2) | 5-9 (2) | 4-5 (2) | 3-9 (3) |
| Roof, ceiling, one clear-span floor · 2-2 × 12 | 7-9 (2) | 5-11 (2) | 4-11 (3) | 7-2 (2) | 5-7 (2) | 4-8 (3) | 6-9 (2) | 5-3 (3) | 4-5 (3) |
| Roof, ceiling, one clear-span floor · 3-2 × 8 | 6-11 (1) | 5-3 (2) | 4-5 (2) | 6-5 (1) | 5-0 (2) | 4-2 (2) | 6-1 (1) | 4-8 (2) | 4-0 (2) |
| Roof, ceiling, one clear-span floor · 3-2 × 10 | 8-3 (2) | 6-3 (2) | 5-3 (2) | 7-8 (2) | 5-11 (2) | 5-0 (2) | 7-3 (2) | 5-7 (2) | 4-8 (2) |
| Roof, ceiling, one clear-span floor · 3-2 × 12 | 9-8 (2) | 7-5 (2) | 6-2 (2) | 9-0 (2) | 7-0 (2) | 5-10 (2) | 8-6 (2) | 6-7 (2) | 5-6 (3) |
| Roof, ceiling, one clear-span floor · 4-2 × 8 | 8-0 (1) | 6-1 (1) | 5-1 (2) | 7-5 (1) | 5-9 (2) | 4-10 (2) | 7-0 (1) | 5-5 (2) | 4-7 (2) |
| Roof, ceiling, one clear-span floor · 4-2 × 10 | 9-6 (1) | 7-3 (2) | 6-1 (2) | 8-10 (1) | 6-10 (2) | 5-9 (2) | 8-4 (1) | 6-5 (2) | 5-5 (2) |
| Roof, ceiling, one clear-span floor · 4-2 × 12 | 11-2 (2) | 8-6 (2) | 7-2 (2) | 10-5 (2) | 8-0 (2) | 6-9 (2) | 9-10 (2) | 7-7 (2) | 6-5 (2) |
| Roof, ceiling, two center-bearing floors · 1-2 × 6 | 2-8 (2) | 2-1 (2) | 1-10 (2) | 2-7 (2) | 2-0 (2) | 1-9 (2) | 2-5 (2) | 1-11 (2) | 1-8 (2) |
| Roof, ceiling, two center-bearing floors · 1-2 × 8 | 3-5 (2) | 2-8 (2) | 2-4 (3) | 3-3 (2) | 2-7 (2) | 2-2 (3) | 3-1 (2) | 2-5 (3) | 2-1 (3) |
| Roof, ceiling, two center-bearing floors · 1-2 × 10 | 4-0 (2) | 3-2 (3) | 2-9 (3) | 3-10 (2) | 3-1 (3) | 2-7 (3) | 3-8 (2) | 2-11 (3) | 2-5 (3) |
| Roof, ceiling, two center-bearing floors · 1-2 × 12 | 4-9 (3) | 3-9 (3) | 3-2 (4) | 4-6 (3) | 3-7 (3) | 3-1 (4) | 4-3 (3) | 3-5 (3) | 2-11 (4) |
| Roof, ceiling, two center-bearing floors · 2-2 × 4 | 2-8 (1) | 2-1 (1) | 1-9 (1) | 2-6 (1) | 2-0 (1) | 1-8 (1) | 2-5 (1) | 1-11 (1) | 1-7 (1) |
| Roof, ceiling, two center-bearing floors · 2-2 × 6 | 4-0 (1) | 3-2 (2) | 2-8 (2) | 3-9 (1) | 3-0 (2) | 2-7 (2) | 3-7 (1) | 2-10 (2) | 2-5 (2) |
| Roof, ceiling, two center-bearing floors · 2-2 × 8 | 5-0 (2) | 4-0 (2) | 3-5 (2) | 4-10 (2) | 3-10 (2) | 3-3 (2) | 4-7 (2) | 3-7 (2) | 3-1 (2) |
| Roof, ceiling, two center-bearing floors · 2-2 × 10 | 6-0 (2) | 4-9 (2) | 4-0 (2) | 5-8 (2) | 4-6 (2) | 3-10 (3) | 5-5 (2) | 4-3 (2) | 3-8 (3) |
| Roof, ceiling, two center-bearing floors · 2-2 × 12 | 7-0 (2) | 5-7 (2) | 4-9 (3) | 6-8 (2) | 5-4 (3) | 4-6 (3) | 6-4 (2) | 5-0 (3) | 4-3 (3) |
| Roof, ceiling, two center-bearing floors · 3-2 × 8 | 6-4 (1) | 5-0 (2) | 4-3 (2) | 6-0 (1) | 4-9 (2) | 4-1 (2) | 5-8 (2) | 4-6 (2) | 3-10 (2) |
| Roof, ceiling, two center-bearing floors · 3-2 × 10 | 7-6 (2) | 5-11 (2) | 5-1 (2) | 7-1 (2) | 5-8 (2) | 4-10 (2) | 6-9 (2) | 5-4 (2) | 4-7 (2) |
| Roof, ceiling, two center-bearing floors · 3-2 × 12 | 8-10 (2) | 7-0 (2) | 5-11 (2) | 8-5 (2) | 6-8 (2) | 5-8 (3) | 8-0 (2) | 6-4 (2) | 5-4 (3) |
| Roof, ceiling, two center-bearing floors · 4-2 × 8 | 7-3 (1) | 5-9 (1) | 4-11 (2) | 6-11 (1) | 5-6 (2) | 4-8 (2) | 6-7 (1) | 5-2 (2) | 4-5 (2) |
| Roof, ceiling, two center-bearing floors · 4-2 × 10 | 8-8 (1) | 6-10 (2) | 5-10 (2) | 8-3 (2) | 6-6 (2) | 5-7 (2) | 7-10 (2) | 6-2 (2) | 5-3 (2) |
| Roof, ceiling, two center-bearing floors · 4-2 × 12 | 10-2 (2) | 8-1 (2) | 6-10 (2) | 9-8 (2) | 7-8 (2) | 6-7 (2) | 9-2 (2) | 7-3 (2) | 6-2 (2) |
| Roof, ceiling, two clear-span floors · 1-2 × 6 | 2-3 (2) | 1-9 (2) | 1-5 (2) | 2-3 (2) | 1-9 (2) | 1-5 (3) | 2-2 (2) | 1-8 (2) | 1-5 (3) |
| Roof, ceiling, two clear-span floors · 1-2 × 8 | 2-10 (2) | 2-2 (3) | 1-10 (3) | 2-10 (2) | 2-2 (3) | 1-10 (3) | 2-9 (2) | 2-1 (3) | 1-10 (3) |
| Roof, ceiling, two clear-span floors · 1-2 × 10 | 3-4 (2) | 2-7 (3) | 2-2 (3) | 3-4 (3) | 2-7 (3) | 2-2 (4) | 3-3 (3) | 2-6 (3) | 2-2 (4) |
| Roof, ceiling, two clear-span floors · 1-2 × 12 | 4-0 (3) | 3-0 (3) | 2-7 (4) | 4-0 (3) | 3-0 (4) | 2-7 (4) | 3-10 (3) | 3-0 (4) | 2-6 (4) |
| Roof, ceiling, two clear-span floors · 2-2 × 4 | 2-3 (1) | 1-8 (1) | 1-4 (1) | 2-3 (1) | 1-8 (1) | 1-4 (1) | 2-2 (1) | 1-8 (1) | 1-4 (2) |
| Roof, ceiling, two clear-span floors · 2-2 × 6 | 3-4 (1) | 2-6 (2) | 2-2 (2) | 3-4 (2) | 2-6 (2) | 2-2 (2) | 3-3 (2) | 2-6 (2) | 2-1 (2) |
| Roof, ceiling, two clear-span floors · 2-2 × 8 | 4-3 (2) | 3-3 (2) | 2-8 (2) | 4-3 (2) | 3-3 (2) | 2-8 (2) | 4-1 (2) | 3-2 (2) | 2-8 (3) |
| Roof, ceiling, two clear-span floors · 2-2 × 10 | 5-0 (2) | 3-10 (2) | 3-2 (3) | 5-0 (2) | 3-10 (2) | 3-2 (3) | 4-10 (2) | 3-9 (3) | 3-2 (3) |
| Roof, ceiling, two clear-span floors · 2-2 × 12 | 5-11 (2) | 4-6 (3) | 3-9 (3) | 5-11 (2) | 4-6 (3) | 3-9 (3) | 5-8 (2) | 4-5 (3) | 3-9 (3) |
| Roof, ceiling, two clear-span floors · 3-2 × 8 | 5-3 (1) | 4-0 (2) | 3-5 (2) | 5-3 (2) | 4-0 (2) | 3-5 (2) | 5-1 (2) | 3-11 (2) | 3-4 (2) |
| Roof, ceiling, two clear-span floors · 3-2 × 10 | 6-3 (2) | 4-9 (2) | 4-0 (2) | 6-3 (2) | 4-9 (2) | 4-0 (2) | 6-1 (2) | 4-8 (2) | 4-0 (3) |
| Roof, ceiling, two clear-span floors · 3-2 × 12 | 7-5 (2) | 5-8 (2) | 4-9 (3) | 7-5 (2) | 5-8 (2) | 4-9 (3) | 7-2 (2) | 5-6 (3) | 4-8 (3) |
| Roof, ceiling, two clear-span floors · 4-2 × 8 | 6-1 (1) | 4-8 (2) | 3-11 (2) | 6-1 (1) | 4-8 (2) | 3-11 (2) | 5-11 (1) | 4-7 (2) | 3-10 (2) |
| Roof, ceiling, two clear-span floors · 4-2 × 10 | 7-3 (2) | 5-6 (2) | 4-8 (2) | 7-3 (2) | 5-6 (2) | 4-8 (2) | 7-0 (2) | 5-5 (2) | 4-7 (2) |
| Roof, ceiling, two clear-span floors · 4-2 × 12 | 8-6 (2) | 6-6 (2) | 5-6 (2) | 8-6 (2) | 6-6 (2) | 5-6 (2) | 8-3 (2) | 6-4 (2) | 5-4 (3) |
IRC 2021 Table R602.7(1), exterior bearing walls: maximum header span in feet-inches and, in brackets, jack studs at each end, for No. 2 Douglas fir-larch, hem-fir, Southern pine and spruce-pine-fir. Columns are ground snow load and building width measured perpendicular to the ridge; widths in between may be interpolated. Interior bearing walls use Table R602.7(2), in the calculator.
Where the numbers come from
- Spans and jack studs: International Residential Code 2021, Tables R602.7(1), exterior bearing walls (five loads from roof and ceiling to two clear-span floors, ground snow 30, 50 and 70 psf, building width 12, 24 and 36 ft), and R602.7(2), interior bearing walls (one or two floors), as printed in the 2021 Seattle Residential Code, which adopts them without a Seattle amendment. No. 2 Douglas fir-larch, hem-fir, Southern pine and spruce-pine-fir. Notes: widths in between may be interpolated; under 30 psf use the 30 psf column; 2 × 8 to 2 × 12 headers not braced on top × 0.70. Read October 26, 2026. 2021 Seattle Residential Code, chapter 6 (PDF)
- The rest is choosing: of the sizes whose span reaches the opening, the one with the least lumber, plies × depth, and then the fewer plies. Between two widths the span is interpolated in a straight line and the jack studs are those of the wider column.
The tables cover sawn lumber, No. 2 grade, in a building no wider than 36 ft. LVL, glulam and steel headers, point loads from a girder truss or a post above, and other grades or species are outside them.
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