Header Size Calculator
Headers carry the load above door and window openings, so using the right size is critical for structural safety. This calculator recommends a header size based on your opening width, whether the wall is load-bearing, and how many stories are above it. Always verify with your local building code or a structural engineer for critical applications.
Header Sizing Rules of Thumb
For standard residential construction with double 2x headers in load-bearing walls supporting one story:
| Opening Span | Header Size | Header Depth |
|---|---|---|
| Up to 4 ft | Double 2x6 | 5.5" |
| 4 to 6 ft | Double 2x8 | 7.25" |
| 6 to 8 ft | Double 2x10 | 9.25" |
| 8 to 10 ft | Double 2x12 | 11.25" |
| Over 10 ft | LVL or steel | Varies |
These are general guidelines based on the IRC (International Residential Code) prescriptive tables for standard residential loading conditions. Your local code may have different requirements.
Load-Bearing vs. Non-Bearing
Load-bearing walls carry weight from the roof, floors, or walls above. They need properly sized headers to transfer that load to the jack studs and down to the foundation.
Non-bearing walls (partition walls) only support the weight of the wall itself. Headers in these walls can be much smaller -- often a double 2x4 is sufficient for spans up to 6 feet.
Header Construction Methods
Double 2x lumber: Two pieces of dimensional lumber with a 1/2" plywood spacer to match 2x4 wall thickness (3.5"). This is the most common residential method.
LVL (Laminated Veneer Lumber): Engineered beams that can span greater distances with less depth. More expensive but necessary for wide openings like sliding glass doors.
Steel: Required for very wide openings (16+ feet) or heavy loads. Must be specified by a structural engineer.
Jack Stud Requirements
Jack studs (also called trimmer studs) sit under each end of the header and transfer the load down. Wider openings need more jack studs:
- Spans under 4 ft: 1 jack stud per side
- Spans 4-8 ft: 2 jack studs per side
- Spans over 8 ft: 3 jack studs per side