Lintel Header Size Calculator
Plan your structural engineering project with our free lintel header size calculator. Get precise measurements, material lists, and budgets.
Formula
M = wL2/8 | Required S = M/Fb | Check delta <= L/360
The header is modeled as a simply supported beam carrying a uniform load equal to the total tributary dead and live loads from above. The bending moment is wL-squared over 8. The required section modulus S is the moment divided by the allowable bending stress. The header must also satisfy the deflection limit of L/360 to prevent cracking in finishes above the opening.
Worked Examples
Example 1: 6-Foot Window in One-Story Wall
Problem: Determine the header size for a 6-foot window opening in a one-story exterior bearing wall with 30 psf total roof load.
Solution: Roof tributary = 6 ft, Wall DL = 7 * 8 = 56 plf\nTotal = 30 * 6 + 56 = 236 plf\nSpan = 6.25 ft, M = 236 * 6.25^2 / 8 = 1,152 ft-lb\nRequired S = 1152 * 12 / 1200 = 11.52 in3\n2-2x8 has S = 26.28 -> PASS
Result: Recommended: 2-2x8 header
Example 2: 8-Foot Door in Two-Story Wall
Problem: Size a header for an 8-foot garage door opening with two stories of load above.
Solution: Floor load = 50 * 6 = 300, Roof = 30 * 6 = 180, Wall = 56 * 2 = 112\nTotal = 592 plf, Span = 8.25 ft\nM = 592 * 8.25^2 / 8 = 5,036 ft-lb\nRequired S = 5036 * 12 / 1200 = 50.36 in3\n3-2x10 has S = 64.17 -> PASS
Result: Recommended: 3-2x10 header
Frequently Asked Questions
How do I determine the correct header size for a window or door opening?
Header size depends on the opening width, the loads being supported, and the lumber grade. For one-story exterior walls with standard roof loads, a doubled 2x8 header typically handles openings up to 6 feet, while a doubled 2x10 can span up to 8 feet. For two-story loads or wider openings, doubled 2x12 or triple-ply headers may be needed. The key is to calculate the total load per linear foot on the header, then check that both the bending stress and deflection are within allowable limits.
What loads does a header carry?
A header carries all loads from above the opening down to the jack studs at each side. For a bearing wall, this includes the roof dead and live loads, any floor loads from stories above, and the weight of the wall framing itself. The tributary width of the roof or floor load is typically half the joist span on each side. For a non-bearing interior wall, the header only carries the weight of the wall framing and any finishes above the opening, which is much lighter.
What is the difference between a lintel and a header?
In wood-frame construction, a header is a horizontal structural member placed above a window or door opening in a wall to transfer loads around the opening to the jack studs. A lintel serves the same purpose but is more commonly used in masonry construction, where it spans across the top of an opening in a brick or block wall. In practice, the terms are often used interchangeably in residential construction. Steel lintels or angle iron are common in masonry, while wood or engineered lumber headers are standard in framed walls.
How do I size an HVAC system for a building?
HVAC sizing uses Manual J calculations considering square footage, insulation, window area, climate zone, and occupancy. A rough estimate is 1 ton of cooling per 400-600 square feet. Oversized systems short-cycle and waste energy; undersized systems cannot maintain comfort.
What formula does Lintel Header Size Calculator use?
The formula used is described in the Formula section on this page. It is based on widely accepted standards in the relevant field. If you need a specific reference or citation, the References section provides links to authoritative sources.
Is my data stored or sent to a server?
No. All calculations run entirely in your browser using JavaScript. No data you enter is ever transmitted to any server or stored anywhere. Your inputs remain completely private.