Joist Span Calculator

Pick your lumber size, spacing, and load to find the maximum allowed floor joist span. Estimates follow typical IRC span table values for #2 lumber.

ft

🧭 Code-based

Estimates follow IRC R502.3 floor joist span tables for #2 graded lumber.

🔖 Adjustable

Spacing, live load, dead load, and species all change the allowed span.

📐 Quick check

Compare your planned span to the max and get the next joist size up if needed.

🔒 Private

All calculations run locally in your browser.

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