Free Tool
Free beam and header span calculator
Pick your beam or header make-up, the load it carries, and the species to get a reference maximum span. A starting reference, not a stamped design. Free, no signup.
Private by design — everything you type stays in your browser. Nothing is uploaded, stored, or seen by us.
How far a header can carry
A header over a door or window, or a beam under a floor, can only span so far before it needs a post or a bigger member. This gives you a reference number to plan around and to sanity-check what is already in place.
The two things that move the span most are the make-up and the load. A built-up header of three 2x12s carries much farther than two 2x8s, and a header holding up roof alone spans well past one carrying a floor on top of it, since the floor load is heavier and constant.
Species matters too. Southern Pine is stiffer than SPF or Hem-Fir at the same size, so it reaches a bit farther, which the species toggle reflects.
Treat every number here as a ballpark for a common residential case, roughly in line with the IRC tables for a moderate building width and snow load. Wider buildings, heavier snow, and any point load shorten the span fast. This is a reference only. Size a real beam to your local code and the actual tributary load, and bring in an engineer for anything long, heavy, or out of the ordinary.
Beam Span Calculator questions
How far can a beam span?
It depends on the make-up, the load it carries, and the species. This gives a reference max span for common residential headers and beams.
Does a floor above change the span?
A lot. A header carrying roof alone spans well past one carrying roof plus a floor, since the floor load is heavier.
Can I build to these numbers?
Treat them as a starting reference, not a design. Size to your local code and the real tributary load, and get an engineer for anything unusual.
Is this really free?
Yes. No email, no signup, and nothing you type leaves your browser.
Price the whole job fast
Werx turns your takeoff into a branded estimate and proposal in one step, then tracks the real cost as you build. 14-day free trial, no credit card.
No credit card required · Free migration assistance · Cancel anytime
Disclaimer: These free tools and templates are provided for general information and estimating purposes only. All results — including quantities, material and cost estimates, load, sizing, and span figures, scores, and any guidance or warnings — are rough approximations that may not fit your specific project, site conditions, local building codes, or current prices. They are not engineering, architectural, structural, legal, financial, or other professional advice, and are not a substitute for a licensed engineer, architect, contractor, or other qualified professional. Always confirm quantities, sizing, and structural, electrical, mechanical, and code requirements with a licensed professional and your local authority having jurisdiction before purchasing materials or performing any work. Werx makes no warranty as to accuracy and accepts no liability for any decision made using these tools. Use at your own risk. See our Terms of Service.