Header Calculator
Size door and window headers the right way
Width of door or window opening
Bearing walls carry roof/floor loads
Nominal stud depth (6" = 2x6 wall)
Lumber Pieces
—
pieces
Jack Studs
—
per side
Header Size
—
nominal
Disclaimer: Results are estimates based on standard formulas. Not a substitute for professional advice from a licensed contractor, engineer, or architect. Verify all calculations before making purchasing or construction decisions.
How to Use This Calculator
Framing a door or window? The header carries the load above the opening, so getting the size right matters for safety. Our calculator picks header depth, lumber count, and jack studs based on span and wall type.
- Measure the rough opening width in feet
- Decide if the wall is load-bearing or non-bearing
- Enter the opening width, wall type, and wall thickness
- Use the recommended header size and add cripple studs above
Expert Insights
Smart analysis for your Header project
Span-Based Sizing
Header depth grows with the opening: 2x4 up to 4 ft, 2x6 up to 6 ft, and 2x8 beyond on bearing walls. Non-bearing walls use a 2x4 minimum.
Load Path Smarts
Load-bearing walls carry roof or floor loads above. Always confirm with a pro before modifying — getting this wrong causes sagging and structural failure.
Jack Stud Logic
Wider openings concentrate more load at each side. Openings under 5 ft use one jack stud per side; wider openings need two for proper support.
Calculation Formula
Header depth (in) = Bearing: < 4 ft → 4 | < 6 ft → 6 | else → 8
Non-bearing: always 4
Lumber pieces = 2 (doubled header)
Jack studs = opening < 5 ft → 1 per side | else → 2 per side
Header size = 2 x [depth] (double)
Header Material Comparison
| Material | Typical Use | Cost | Strength | Notes |
|---|---|---|---|---|
| Douglas Fir 2x Lumber | Standard residential headers | $ | Good | Easy to cut and nail on site |
| LVL (Laminated Veneer Lumber) | Long spans, heavy loads | $$$ | Excellent | Engineered, predictable strength |
| Glulam Beam | Very large openings | $$$$ | Excellent | Custom sizes, architectural look |
Authority References
Our calculations are based on guidelines and standards from these authoritative sources:
- American Wood Council (AWC) — Span Tables for Joists and Rafters & Wood Frame Construction Manual. Learn more
- International Residential Code (IRC) — Section R602.7 — Headers. Learn more
- National Design Specification (NDS) for Wood Construction — Design Values for Wood Construction. Learn more
Frequently Asked Questions
What size header do I need for a 6 foot opening?
For a 6 foot load-bearing opening, a double 2x8 header is standard. For non-bearing walls, a double 2x4 header is usually enough.
How many jack studs does a header need?
Openings under 5 feet typically need one jack stud per side. Wider openings usually need two jack studs per side to carry the concentrated load down to the plate.
Why are headers doubled?
Headers are built from two pieces of lumber nailed together so they can span the opening and carry loads from above. The doubled thickness also matches standard wall stud width.