Header Span Calculator
How far a header spans over a door or window: enter the opening, the wall and what it holds up, and see the smallest built-up 2x header that works and the jack studs it needs, with the longest span of every header.
A 2-2x10 header spans a 6′ opening, using 75% of its capacity (limited by bending), on 1 jack stud at each end.
The 2-2x10 over the opening, on its jack studs, with the load each end puts on them.
The roof the header holds up.
Longest span, Douglas Fir-Larch No.2
| Header | 2 plies | 3 plies |
|---|---|---|
| 2x6 | 4′ 5″ (1) | 5′ 5″ (1) |
| 2x8 | 5′ 8″ (1) | 6′ 11″ (1) |
| 2x10 | 6′ 11″ (1) | 8′ 5″ (1) |
| 2x12 | 8′ (1) | 9′ 10″ (1) |
Jack studs at each end in brackets. Spans in bold reach 6′.
Over a 6′ opening, 2 plies
| 2-2x6Fails bending | 179% |
| 2-2x8Fails bending | 112% |
| 2-2x10Works, 1 jack stud | 75% |
| 2-2x12Works, 1 jack stud | 56% |
Every check for the 2-2x10
| Bending | 75% |
| Shear | 53% |
| Live and roof load deflection (span/360) | 21% |
| Total load deflection (span/240) | 21% |
The header carries 225 lb/ft dead load and 450 lb/ft snow, and puts 2,025 lb on each end.
Size the rafters above Check the 2-2x10 in the beam designer
An exterior bearing wall of a 28′ wide building holding up the roof, with 30 psf snow. The beam designer link treats the snow as live load, without the load duration factor, so it allows a little less.
Header span tables
The longest span for Douglas Fir-Larch No.2 headers in an exterior bearing wall, by building width, with 15 psf roof dead load and a 1′ overhang. The number in brackets is the jack studs at each end. Floors bear on a wall down the middle. Worked out by the calculator, not copied from the code tables.
Roof and ceiling, 30 psf snow
| Header | 20 ft wide | 28 ft wide | 36 ft wide |
|---|---|---|---|
| 2-2x6 | 5′ 2″ (1) | 4′ 5″ (1) | 3′ 11″ (1) |
| 2-2x8 | 6′ 7″ (1) | 5′ 8″ (1) | 5′ (1) |
| 2-2x10 | 8′ 1″ (1) | 6′ 11″ (1) | 6′ 1″ (1) |
| 2-2x12 | 9′ 4″ (1) | 8′ (1) | 7′ 1″ (2) |
| 3-2x6 | 6′ 4″ (1) | 5′ 5″ (1) | 4′ 10″ (1) |
| 3-2x8 | 8′ 1″ (1) | 6′ 11″ (1) | 6′ 2″ (1) |
| 3-2x10 | 9′ 11″ (1) | 8′ 5″ (1) | 7′ 6″ (1) |
| 3-2x12 | 11′ 6″ (1) | 9′ 10″ (1) | 8′ 9″ (1) |
Roof, ceiling and one floor, 30 psf snow
| Header | 20 ft wide | 28 ft wide | 36 ft wide |
|---|---|---|---|
| 2-2x6 | 4′ 3″ (1) | 3′ 8″ (1) | 3′ 4″ (1) |
| 2-2x8 | 5′ 5″ (1) | 4′ 8″ (1) | 4′ 2″ (1) |
| 2-2x10 | 6′ 8″ (1) | 5′ 9″ (1) | 5′ 2″ (2) |
| 2-2x12 | 7′ 8″ (1) | 6′ 8″ (2) | 6′ (2) |
| 3-2x6 | 5′ 3″ (1) | 4′ 7″ (1) | 4′ 1″ (1) |
| 3-2x8 | 6′ 8″ (1) | 5′ 9″ (1) | 5′ 2″ (1) |
| 3-2x10 | 8′ 2″ (1) | 7′ 1″ (1) | 6′ 4″ (1) |
| 3-2x12 | 9′ 5″ (1) | 8′ 2″ (1) | 7′ 4″ (2) |
Roof and ceiling, 50 psf snow
| Header | 20 ft wide | 28 ft wide | 36 ft wide |
|---|---|---|---|
| 2-2x6 | 4′ 4″ (1) | 3′ 8″ (1) | 3′ 3″ (1) |
| 2-2x8 | 5′ 6″ (1) | 4′ 8″ (1) | 4′ 2″ (1) |
| 2-2x10 | 6′ 8″ (1) | 5′ 9″ (1) | 5′ 1″ (2) |
| 2-2x12 | 7′ 9″ (1) | 6′ 8″ (2) | 5′ 11″ (2) |
| 3-2x6 | 5′ 4″ (1) | 4′ 6″ (1) | 4′ (1) |
| 3-2x8 | 6′ 9″ (1) | 5′ 9″ (1) | 5′ 1″ (1) |
| 3-2x10 | 8′ 3″ (1) | 7′ (1) | 6′ 3″ (1) |
| 3-2x12 | 9′ 6″ (1) | 8′ 2″ (1) | 7′ 3″ (2) |
Roof, ceiling and one floor, 50 psf snow
| Header | 20 ft wide | 28 ft wide | 36 ft wide |
|---|---|---|---|
| 2-2x6 | 3′ 10″ (1) | 3′ 4″ (1) | 3′ (1) |
| 2-2x8 | 4′ 11″ (1) | 4′ 3″ (1) | 3′ 9″ (1) |
| 2-2x10 | 6′ (1) | 5′ 2″ (2) | 4′ 7″ (2) |
| 2-2x12 | 6′ 11″ (2) | 6′ (2) | 5′ 4″ (2) |
| 3-2x6 | 4′ 9″ (1) | 4′ 1″ (1) | 3′ 8″ (1) |
| 3-2x8 | 6′ (1) | 5′ 2″ (1) | 4′ 8″ (1) |
| 3-2x10 | 7′ 4″ (1) | 6′ 4″ (1) | 5′ 8″ (2) |
| 3-2x12 | 8′ 6″ (1) | 7′ 4″ (2) | 6′ 7″ (2) |
For other species, grades and loads, use the calculator above.
How the calculator works out a header span
Each header is a simple span checked to the 2018 National Design Specification (NDS) for wood, with allowable stress design (ASD), as dry lumber. Its load comes from the building's width, like the header tables in the International Residential Code (IRC R602.7):
- Roof: the dead load and snow or roof live load over half the building's width plus the overhang, with rafters or trusses that span from wall to wall.
- Each floor above: 15 psf dead and 40 psf live load over a quarter of the width when the joists bear on a wall in the middle, or half when they span the building, plus 90 lb/ft for that story's wall.
The header passes when it meets every check under each load combination of ASCE 7-16:
- Bending and shear, with the load duration factor for the shortest load in the combination: 0.9 for dead load alone, 1.0 with floor live load, 1.15 with snow and 1.25 with roof live load.
- Deflection: under live and roof load up to the span over 360, and under total load up to the span over 240.
- Jack studs carry the end of the header. Each gives 1.5 in of bearing across the header's width, at the wood's allowable crushing stress across the grain.
The plies are nailed together but don't take the 1.15 factor that joists and rafters sharing load through sheathing do, so these spans are a little shorter than some tables.
Header questions
What size header for a 6 ft opening?
In a 2x4 wall of a 28 ft wide, one-story house with 30 psf of snow, a 2-2x10; for the first floor of the same house with a second floor above, a 2-2x12. In a 2x6 wall, a 3-2x8 for the one-story house and a 3-2x10 with a floor above.
What size header for a 3 ft door?
In a 2x4 wall of a 28 ft wide, one-story house with 30 psf of snow, a 2-2x6; with a floor above, a 2-2x6.
What size header for an 8 ft opening?
In a 2x4 wall of a 28 ft wide, one-story house with 30 psf of snow, a 2-2x12; in a 2x6 wall, a 3-2x10.
What about a 16 ft garage door?
No 2x header spans 16 ft in a 2x6 wall of a 28 ft wide, one-story house with 30 psf of snow. Long openings usually take a glulam or laminated veneer lumber (LVL) beam; check one in the beam designer.
How many jack studs does a header need?
Enough to carry its end without crushing the wood across the grain: usually one for short headers and two for long or heavily loaded ones. The calculator gives the number for each header.
How do the plies fit the wall?
Two 2x plies are 3 in thick, so in a 2x4 wall they take a 1/2 in plywood spacer to fill the 3-1/2 in. Three plies are 4-1/2 in, which fits a 2x6 wall with room for a strip of insulation.
Does a wall that holds nothing up need a header?
Not a structural one: a non-bearing wall can use a single flat 2x over the opening. To check the rafters above, use the rafter span calculator; for a beam on its own, the wood beam span calculator.