Wood Beam Calculator
Size beams from span and load
Clear span between supports
Uniform load (40 lb/ft typical)
Solid sawn or engineered LVL
Section Modulus
—
in³
Estimated Cost
—
USD
Recommended Size
—
nominal
Disclaimer: Results are estimates based on standard formulas. Not a substitute for professional advice from a licensed contractor, engineer, or architect. Verify all calculations before making purchasing or construction decisions.
How to Use This Calculator
Picking a beam for a floor, deck, or header? Span and load drive the size. Our calculator recommends a beam size, computes the bending moment (section modulus), and estimates cost for solid sawn or LVL.
- Measure the clear span between supports in feet
- Estimate the uniform load per foot (40 lb/ft is typical residential)
- Choose solid sawn or LVL beam type
- Have an engineer confirm for large spans or heavy loads
Expert Insights
Smart analysis for your Beam project
Span-Based Sizing
Shorter spans use smaller beams: 2x8 up to 8 ft, 2x10 up to 12 ft, 2x12 up to 16 ft, and a 3-ply 2x12 built-up beam for longer runs.
LVL Advantage
LVL carries about 2x the load of solid sawn at the same size. It costs more but allows longer spans and tighter tolerances.
Moment Check
Our calculator uses M = (w × L²) / 8 for a uniformly loaded beam. Compare this to allowable fiber stress to verify the beam is adequate.
Calculation Formula
Recommended size = span < 8 ft → 2x8 | < 12 ft → 2x10 | < 16 ft → 2x12 | else → 3-ply 2x12
Section modulus = (Load per ft × Span²) / 8
Estimated cost = Ceiling(Span × ($30 LVL | $15 solid sawn))
Beam Material Comparison
| Material | Relative Strength | Cost per ft | Max Span (typical) | Best Use |
|---|---|---|---|---|
| Solid Sawn (DF/LF) | 1.0x | $15 | ~16 ft | Standard residential |
| LVL (Engineered) | ~2.0x | $30 | ~24+ ft | Long spans, heavy loads |
| Glulam | ~2.5x | $45+ | 30+ ft | Large openings, exposed |
Authority References
Our calculations are based on guidelines and standards from these authoritative sources:
- American Wood Council (AWC) — Beam Design Formulas & Span Tables. Learn more
- National Design Specification (NDS) for Wood Construction — Supplement Design Values. Learn more
- International Residential Code (IRC) — Section R502.5 — Girder Spans & Beam Tables. Learn more
Frequently Asked Questions
How do I size a wood beam?
Beam size depends on span and load. As a rule of thumb, use a 2x8 up to 8 ft spans, 2x10 up to 12 ft, 2x12 up to 16 ft, and a 3-ply 2x12 built-up beam for longer spans. Always confirm with span tables or an engineer.
What is stronger, LVL or solid sawn lumber?
LVL (Laminated Veneer Lumber) is stronger and more dimensionally stable than solid sawn lumber. It allows longer spans and heavier loads with predictable performance, but costs about twice as much.
What is the formula for beam moment?
For a uniformly loaded simply supported beam, the maximum bending moment is M = (w × L²) / 8, where w is the load per foot and L is the span in feet. Divide by allowable fiber stress to find required section modulus.