Door Header Size Calculator
Construction & Home ImprovementEstimate a recommended header size for a door or window opening using the standard framing rule of thumb.
Required Nominal Header Depth
Approximate required nominal header depth, in inches, using the times-12 rule of thumb.
Recommended Header
(2) 2x6
Nearest standard doubled header size at or above the required depth.
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Construction & Home Improvement calculators
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Creators
Odeh Ahwal0people find this calculator helpful
Views
Helpful
Saved
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Construction & Home Improvement calculators
Frequently Asked Questions
How does this rule of thumb work?
It uses a widely cited simplified framing rule: the maximum span in inches roughly equals the header depth in inches times 12. Written the other way, the required nominal header depth in inches approximately equals the opening span in feet, so a 6 foot opening suggests a nominal 6 inch deep header, commonly built as two 2 by 6 members fastened together.
Is this accurate enough to build from?
Treat this as a rough starting estimate only, useful for early planning. It does not account for species, snow load, the width of the building, or the number of floors bearing on the header, all of which affect the real required size in IRC prescriptive header tables or an engineer-designed header. For anything beyond a small, low-load opening, check the local prescriptive span table or consult a structural engineer or the local building department.
Why is the required depth in inches the same number as the opening in feet?
That is a direct result of the times-12 rule: since there are 12 inches in a foot, a maximum span in inches equal to depth times 12 is mathematically the same statement as a maximum span in feet equal to depth in inches. It is a consequence of the rule itself, not a separate calculation.
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