Header Size Calculator
Enter the rough opening width, what the wall carries, the building width and the roof snow load. The calculator works out the load on the header, picks the smallest 2-ply or 3-ply 2× header that passes, and tells you how many jack and king studs to use.
- 2× header size
- Jack studs
- Load per foot
This sizes sawn Douglas fir-larch No. 2 headers in light timber framing. Masonry and steel openings need a lintel instead.
Wider openings and heavier loads need deeper headers. A header carries the roof and floors above an opening down to the jack studs. In a 28 ft wide house with a 30 psf snow load and only the roof above, a 6 ft opening needs about a 2-ply 2×10, while a 3 ft opening gets by with a 2-ply 2×6.
Header size chart
Roof only, 30 psf snow. Search for an opening.
| Opening (ft) | 20 ft building | 28 ft building | 36 ft building |
|---|---|---|---|
| 2 | 2-ply 2×6 | 2-ply 2×6 | 2-ply 2×6 |
| 3 | 2-ply 2×6 | 2-ply 2×6 | 2-ply 2×6 |
| 4 | 2-ply 2×6 | 2-ply 2×6 | 2-ply 2×8 |
| 5 | 2-ply 2×6 | 2-ply 2×8 | 2-ply 2×8 |
| 6 | 2-ply 2×8 | 2-ply 2×10 | 2-ply 2×10 |
| 7 | 2-ply 2×10 | 2-ply 2×12 | 2-ply 2×12 |
| 8 | 2-ply 2×10 | 2-ply 2×12 | 3-ply 2×12 |
| 10 | 3-ply 2×12 | LVL | LVL |
Douglas fir-larch No. 2, estimates only.
Opening width and header
28 ft building, roof only, 30 psf snow. Slide the opening width.
The wall drawing shows the header on its jack studs, with king studs on the outside.
How to size a header
Load to lumber. Step through it.
Measure the opening
Rough opening width.
A point load, such as a girder truss or post landing on the header, needs an engineer rather than a table.
Sawn lumber, LVL or flat header
Header types. Compare them.
Two or three plies.
Engineered.
Non-bearing.
Insulated headers with rigid foam between the plies cut heat loss in exterior walls.
Before framing
Header checks. Tick each item.
Tick each item as you go.
Check your local building code span tables, which may differ with lumber species, grade and snow load.
What you get
Header sizing. Each tile explains one result.
Plies and depth.
Per foot.
Per cent.
Each side.
Each side.
Headers sag over time if undersized, which can crack drywall and jam doors.
Frequently Asked Questions
No question matches that search.
What size header do I need for a six foot opening?
In a typical house carrying only the roof, about a two-ply two by ten. Heavier snow or floors above need more.
How many jack studs does a header need?
One each side for most openings up to about six feet, and two for wider or heavily loaded ones.
Does a non-load-bearing wall need a header?
Only a light one, such as a flat two by four, to frame the opening.
What is the difference between a header and a lintel?
They do the same job. Header is the usual word in timber stud walls, lintel in masonry.
When should I use an LVL header?
When sawn lumber is not deep enough, usually for openings over about eight feet or with floors above.
What is a king stud?
The full-height stud beside the jack stud that runs from plate to plate.
How long should the header be?
The opening width plus the width of the jack studs at both ends, usually three inches more.
Frame openings with confidence
Size the header for the load it really carries, set it on proper jack studs and check against your local code.
More size calculators
Each one has its own calculator, worked examples and answers to common questions.