Deck Beam Calculator
Calculate deck beam size and support requirements
Joist span in feet
Width supported by beam
Tables vary by species
Beam Size
—
ply x dimension
Max Post Spacing
—
ft
Posts Needed
—
posts
How to Use This Calculator
Deck beams support the entire deck structure. Our calculator determines correct beam size and post spacing based on IRC tables.
- Determine joist span
- Choose lumber species
- Use calculator for beam size
- Plan posts and footings
AI Insights
Smart analysis for your project
Smart Estimates
Our AI cross-references material costs, regional pricing, and project complexity for more accurate estimates.
Waste Optimization
AI-calculated waste factors based on project type, not flat percentages. Saves 5-15% on material costs.
Best Practices
Recommendations derived from building codes, contractor data, and thousands of completed projects.
Calculation Formula
IRC Table R507.5: Beam size based on joist span and species
Post spacing from IRC table
Frequently Asked Questions
What size beam for 10 ft joist span?
For 10 ft joist span with SP lumber, use (2) 2x8 beam with posts max 6 ft apart.
How far apart should deck beam posts be?
4-8 ft depending on beam size. (2)2x8 beams max 6 ft, (3)2x8 max 10 ft per IRC.