Header Size Calculator
Find the right header size for your door or window opening.
Header Size Guide — Load-Bearing Walls
1 story supported, 28' building width, Douglas Fir #2
| Opening Width | Header Size | Jack Studs | Material |
|---|---|---|---|
| Up to 4' | (2) 2×6 | 1 each side | Dimensional lumber |
| 4' – 6' | (2) 2×8 | 1 each side | Dimensional lumber |
| 6' – 8' | (2) 2×10 | 2 each side | Dimensional lumber |
| 8' – 10' | (2) 2×12 | 2 each side | Dimensional lumber |
| 10' – 12' | 3.5×9.25" LVL | 2 each side | LVL |
| 12' – 16' | 3.5×11.875" LVL | 3 each side | LVL |
How We Calculate This
This header size calculator uses established formulas and industry-standard data to provide accurate estimates.
- Enter your specific values into the calculator fields above
- Our algorithm applies the relevant formulas using your inputs
- Results are calculated instantly in your browser — nothing is sent to a server
- Review the detailed breakdown to understand how each factor affects your result
These calculations are estimates based on standard formulas. For critical decisions, always consult a qualified professional.
How to Convert Oven Recipes to Air Fryer
This calculator determines header size based on IRC prescriptive tables for residential construction. Header size depends on opening width, the number of stories supported, and whether the wall is load-bearing.
The basic rule:
- Non-bearing walls: a flat 2×4 is adequate for openings up to 8 feet
- Bearing walls supporting 1 story: doubled 2×6 for up to 4', doubled 2×8 for 5-6', doubled 2×10 for 7-8', doubled 2×12 for 9-10'
- Bearing walls supporting 2 stories: header sizes increase by one lumber size
- Each side requires jack studs: 1 jack stud per 4' of opening width (minimum 1)
- King studs flank the jack studs, and cripple studs fill above the header to the top plate
Headers in 2×6 walls can be insulated headers (header plus rigid foam) for better energy efficiency. For openings wider than 12 feet, an LVL or steel header is typically required. Always confirm with local building codes.
When Would You Use This Calculator?
This header size calculator is designed for anyone who needs quick, reliable estimates without complex spreadsheets or professional consultations.
- When you need a quick estimate before committing to a purchase or project
- When comparing different options or scenarios side by side
- When planning a budget and need to understand potential costs
- When you want to verify a quote or estimate you've received from a professional
- When teaching or learning about the concepts behind these calculations
Frequently Asked Questions
What size header do I need for a 6-foot opening?
For a 6-foot opening in a load-bearing wall supporting one story above: doubled 2×8 minimum for a 28' building width, or doubled 2×10 for wider buildings. For non-bearing walls, a flat 2×4 is sufficient regardless of opening width (up to 8').
Do non-bearing walls need headers?
Technically, non-bearing walls only need a flat 2×4 across the top of the opening. However, many builders install a full header anyway for uniformity and to provide a solid nailing surface. Some inspectors may require a code-sized header in all walls.
What is the difference between a king stud and a jack stud?
King studs are full-height studs that run from the bottom plate to the top plate on each side of an opening. Jack studs (trimmers) are shorter studs that sit under the header ends and transfer the header load to the bottom plate. Both are required at every opening.
How wide can a door opening be without a steel header?
With dimensional lumber, doubled 2×12 headers can span up to about 10-12 feet in typical residential loading. LVL headers extend this to 16 feet. Beyond that, a steel angle or W-beam is usually necessary. Garage door openings (16') typically need an LVL or steel header.
Can I use a single 4×8 instead of doubled 2×8?
While a 4×8 has similar dimensions, it is not equivalent to a doubled 2×8 header. The IRC span tables are based on doubled 2× lumber. A solid 4× has a different grain pattern and different allowable stresses. Stick with doubled 2× or engineered lumber (LVL).
What about headers for garage doors?
Standard garage door openings (8-9' single, 16' double) in load-bearing walls typically require an LVL header. A 16-foot garage door usually needs a 3.5×11.875" LVL or similar engineered header. The building width and stories above determine the exact size.