By Zencalcy Editorial TeamLast reviewed About us
A header carries the wall load across an opening and drops it onto the jack studs. Its size depends on the span, the load above and the species: the required section modulus is wL² ÷ (8 Fb), and the depth follows from a chosen width.
Header depth for a door or window opening.
S required = w L² ÷ (8 Fb) d = √(6 S ÷ b)
For a single-storey wall the load is the roof and ceiling tributary plus wall weight; a rough value is 200–400 lb/ft for an exterior wall. Round the depth up to the next nominal lumber size and add jack studs at each end.
| Symbol | Meaning |
|---|---|
| w | Uniform load above the opening. |
| L | Clear span of the opening. |
| Fb | Allowable bending stress. |
The moment is 1,350 lb·ft, or 16,200 lb·in. Required S is 13.5 in³, so a 3-inch-wide header needs a depth of 5.2 inches — a 2 × 6, doubled for a bearing wall.
Continue with the Beam Deflection Calculator, Beam Load Calculator, Bending Stress Calculator, or the Wood Beam Span Calculator — or browse more structural & workshop and all construction calculators.
A doubled 2 × 8 is common for a 6 ft opening in a bearing wall; a single 2 × 6 suits a short non-bearing opening.
Results use standard construction estimating arithmetic: volumes from measured area and depth, unit weights from published material densities, and code-referenced spans or clearances where the page names a code. Quantities are rounded up to whole saleable units and include the stated waste allowance. These tools are planning aids, not structural design, and do not replace a licensed engineer, a local code check, or a contractor's site measurement.
Reference material used to build and check this calculator:
Last reviewed: September 2026. See how we build and check every tool on the about page.
Estimate decking boards by length, screws, hidden fasteners and waste
Calculate concrete blocks needed for wall construction
Calculate full deck materials list including boards, joists, beams, posts, and cost estimates
Price hardwood the way the lumber yard does — by board footage.
Turn measured dimensions into the cubic yards concrete and gravel are sold in.
How many gallons it takes to cover an area at a given depth.
Content updated: September 2026