FLOOR JOIST SPAN
MAX JOIST SPAN
Per IRC R502.3 + AWC tables
RESULT
—
FILL IN ABOVE
Estimate only — based on simplified AWC Maximum Spans for #2 grade lumber, L/360 deflection, 10 psf dead load. Verify with engineer or local code official before framing.
About this calculator
This floor joist span calculator returns the maximum allowable simple span for residential floor joists per IRC R502.3.1 and the American Wood Council Maximum Spans tables. The calculator covers four common joist sizes (2×6 through 2×12), two standard spacings (16 and 24 in OC), the two residential live loads (30 psf for sleeping rooms, 40 psf for living areas), and three common framing species (Doug Fir-Larch, Spruce-Pine-Fir, Southern Pine) — all at #2 grade with L/360 deflection limit and 10 psf dead load. Spans assume a simple span between bearing walls, no cantilever, and no concentrated loads.