Floor Joist Span Calculator

Floor Joist Span Calculator

Determine the maximum allowable span based on joist size and spacing.

* Values are in feet.

Step 1: Enter Joist Details

Select the nominal joist size.

Select the spacing between joists.

The values are based on a simplified span table:
For 16″ O.C. – 2×6: 9.0 ft, 2×8: 12.0 ft, 2×10: 15.0 ft, 2×12: 18.0 ft.
Spacing adjustments available for 12″ and 24″ O.C.