Header & Beam Load Calculator

What this tool does, and what it deliberately doesn't

Sizing a structural header or beam correctly depends on the load it carries, the span it crosses, the species and grade of lumber (or engineered lumber like LVL), and load-duration factors -- all set out in detailed prescriptive span tables in the International Residential Code (IRC), or calculated directly by a licensed engineer for anything outside those tables' scope. This calculator does the first, safe part of that process: converting your opening's width, tributary width, and design loads into the load per linear foot the header or beam actually needs to carry.

It intentionally does not tell you what size lumber to use. The IRC's span tables (for example, Table R602.7.1 for headers) are copyrighted, and more importantly, reading the wrong cell or missing a load-duration adjustment in a table like that can produce a genuinely unsafe result. Getting a beam or header wrong isn't a cosmetic mistake -- it can mean a sagging floor at best, or a structural failure at worst.

What to do with the number this gives you

Take the load-per-linear-foot figure this calculator gives you, along with your span, to one of these:

• The IRC's own header and beam span tables (Section R602.7 and related tables), freely readable online at ICC's Digital Codes library (no account needed for basic read access) -- look up your specific species, grade, and load combination there.
• Your local building department, who can confirm which code edition and any local amendments apply in your jurisdiction.
• A licensed structural engineer, especially for anything outside typical prescriptive situations -- long spans, unusual loading, or load-bearing walls removed during a renovation.

This tool provides a preliminary load estimate for planning purposes only and is not a substitute for the applicable building code's prescriptive tables or a licensed engineer's calculation. Always verify header and beam sizing against your local code and, where required, a licensed professional before construction. Typical dead and live/snow load defaults shown are common starting points, not universal values -- your local code sets the actual required design loads for your area (snow load especially varies enormously by region).