Wood Beam Span Calculator

Estimate the maximum safe span for dimensional wood beams based on lumber species, grade, and live load.

Structural Details

Unit System

Wood Species

Nominal Size

Lumber Grade

Live Load (psf)

psf

Span Recommendation

Ready to size?

Select your lumber type and load conditions to see the recommended maximum span limit.

Overview

Sizing a structural beam correctly is essential for preventing sagging or failure. The span is governed by the modulus of elasticity (flexibility) and the fiber stress in bending of the specific wood species and grade. This calculator provides estimates for residential floor joists at a deflection limit of L/360, based on general American Wood Council (AWC) tables.

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Pro Tips

Spacing beams closer (e.g., 12 inches on center vs 16 inches) significantly increases the weight each beam can carry.
In metric regions, typical spans for 45x190mm lumber approximate the US 2x8 standard.
<strong>Warning:</strong> Always have a licensed structural engineer or local code official verify spans for your specific project.

Fun Facts

"Douglas Fir-Larch is one of the strongest standard framing lumbers used in North America."
"L/360 means the beam will not sag more than its length divided by 360 (e.g., 0.33 inches for a 10-foot span)."
"Nominal 2x10 lumber actually measures 1.5 x 9.25 inches (38 x 235 mm)."

Formula: Span Limit (L) = Function of [(E × I) / (w × L³)] where E is Stiffness and I is Moment of Inertia.

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