Beam Load Calculator
Selecting the right beam for a given span and load is one of the most important structural decisions in construction. This simplified calculator estimates maximum uniform and point loads for common dimensional lumber, LVL (laminated veneer lumber), and steel beams based on allowable bending stress and span length.
Beam capacity is governed by bending stress and deflection. The maximum bending moment a beam can resist is M = Fb × S, where Fb is the allowable bending stress and S is the section modulus (S = bd²/6 for rectangular sections). For uniform loads, M = wL²/8; for center point loads, M = PL/4.
Douglas Fir #2 lumber has an allowable bending stress of about 1,000 psi. LVL (laminated veneer lumber) is significantly stronger at 2,600 psi, making it ideal for headers and long-span beams. Steel W-shapes have allowable bending stresses around 24,000 psi, enabling long spans with compact sections.
Multiple plies increase capacity linearly: a doubled (2-ply) 2x10 beam carries twice the load of a single 2x10. This is common practice for floor girders and headers. For critical structural applications, always have a licensed structural engineer verify beam sizing. This calculator provides estimates based on simplified analysis and does not account for all code requirements including lateral bracing, shear, bearing, and load duration factors.