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Beam Size Calculator - Calculate structural beam dimensions for load support
Calculate structural beam dimensions for load support
Formulas and edge cases are reviewed against authoritative references before publication. For methodology, editorial standards, or corrections, use the links below.
Frequently asked questions
What is tributary width?
The width of floor/roof area supported by the beam, typically half the distance to adjacent supports.
LVL vs dimensional lumber?
LVL (laminated veneer lumber) is stronger and spans further than same-size dimensional lumber.
What is L/360?
Maximum allowable deflection is span/360. A 12ft beam can deflect max 0.4 inches under load.
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About this tool
This Beam Size Calculator turns your inputs into practical results. Provide Beam Span, Tributary Width, and Load Type to calculate Total Load and Minimum Section Modulus.
Adjust values to compare scenarios and see how sensitive the result is. The calculation uses the numbers as entered, so double-check units and expect small differences from rounding in the displayed totals.