Floor Joist Calculator

Choose a span check for dimensional lumber, an engineered I-joist/LVL check, or a quantity-only layout estimate.
Use the preset button above to fill the IRC living-area defaults, or choose custom after editing the load fields.
Measure the unsupported span parallel to the joists, from bearing to bearing.
Measure perpendicular to the joists; this drives joist quantity.
The calculator uses dressed dimensions, such as 1.5 in × 9.25 in for a 2×10.
Leave blank to use the dressed thickness for the nominal size.
Leave blank to use the dressed depth for the nominal size.
Choose a representative engineered-lumber series, then verify final selection in the manufacturer's current guide.
Common residential spacings are 12, 16, 19.2, and 24 inches on center.
Use the code-prescribed load for people, furniture, storage, or deck occupancy.
Permanent weight from framing, subfloor, finishes, ceilings, and fixtures.
L/360 is common for residential floors; larger numbers mean a stiffer floor.
Maximum allowable span 13 ft 11 in (13.88 ft)
Controlling limit state Bending
Actual deflection at entered span 0.621 in
Bending demand/capacity ratio 1.33
Live + dead load on each joist 53.3 plf live + 13.3 plf dead = 66.7 plf per joist
Span status Entered span exceeds the calculated allowable span; choose a deeper/stronger joist, tighter spacing, or engineering review.
Floor joists quantity 10 joists
End/rim joist count 2 rim/end joists
Joist hanger count 20 hangers
Total lineal feet 184.0 ft
Review note Verify final member selection against local code, span tables, and manufacturer literature.
Calculation basis 2x10 Douglas Fir-Larch no 2 at 16 in. o.c.; simply supported uniform-load check.