Find the right header beam dimensions for doors, windows, and wall openings.
| Parameter | Value |
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| Beam Size | Plies | Max Span (ft) | Status |
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Enter the clear span of your opening (the horizontal distance between supports in feet), select how many floors sit above the beam, choose whether the wall is load-bearing, pick your lumber species, and set the number of plies. Hit Calculate and you'll instantly see the minimum recommended beam size plus a table of all valid options.
The tributary width represents how far the roof or floor load extends back toward the center of the structure — typically half the depth of the room or building. For a standard 16-ft deep house, use 8 ft.
Headers are one of the most structurally critical elements in residential framing. Every door, window, and pass-through in a load-bearing wall requires a properly sized header to transfer the weight from above down to the jack studs and king studs on either side. Undersize a header and you risk sagging drywall, sticking doors, cracked finishes — or in severe cases, structural failure.
A common real-world scenario: you're framing a 10-foot garage door opening in a load-bearing wall with one story above it. Many DIYers assume a doubled 2×8 is plenty, but the math may require a 2×12 or even an LVL (laminated veneer lumber) beam depending on the tributary width. Getting this wrong costs thousands to fix after the fact. Conversely, oversizing wastes lumber money — a $400 engineered beam vs. a $60 built-up 2×10 matters on a tight budget.
This calculator uses span tables derived from the IRC (International Residential Code) to give you code-compliant guidance for common lumber species and loading conditions.
The total uniform load on the header is estimated as:
W (plf) = (Floor Load + Roof Load) × Tributary Width
Typical residential loads: 40 psf live + 10 psf dead = 50 psf per floor; roof = 20 psf. Required section modulus S = (W × L²) / (8 × Fb × 12) where Fb is the allowable bending stress for the species/grade, and L is the span in inches. Required moment of inertia I = (5 × W × L⁴) / (384 × E × 0.5 in) limits deflection to L/360. The depth is then chosen from standard lumber sizes (2×6, 2×8, 2×10, 2×12) until both S and I requirements are met.
A header beam spans an opening in a wall — such as a door, window, or archway — and transfers the structural load from above down to the framing members on either side. Without a properly sized header, the weight of the roof or upper floors would have no path to the foundation, causing the opening to deform or collapse over time.
A built-up header is multiple pieces of dimensional lumber (like two 2×10s) nailed or bolted together. LVL (Laminated Veneer Lumber) is an engineered product with higher and more consistent strength values — typically 1.5× to 2× stronger than comparable dimensional lumber. For spans over 10 feet or heavy loads, LVL is usually the better choice despite the higher cost.
No — this tool is designed for residential construction per IRC guidelines. Commercial and multi-family buildings fall under IBC (International Building Code) and typically require a licensed structural engineer to size all headers and beams. Use this as a rough educational reference only for non-residential projects.
Most building codes require some form of header even in non-load-bearing walls, though the requirements are much less stringent. A flat 2×4 or 2×6 on edge is commonly sufficient for openings under 6 feet. Always confirm with your local building department — some jurisdictions allow no header at all for non-bearing partitions.