Deck Joist Calculator is a free, lightweight set of tools for builders and DIYers. You’ll find a deck joist spacing calculator, deck joist span calculator, deck beam size calculator, a cantilever calculator, and recommendations for blocking spacing, plus quick deck joist spacing charts and span charts for planning.
These calculators provide planning estimates only. Structural design depends on lumber species/grade, loads, fasteners, and local amendments. Always verify with official span tables, the International Residential Code (IRC), and manufacturer instructions, and consult your local building department or a licensed professional.
Questions or suggestions? We’re continuously improving these tools.