On-Center Spacing

Definition

On-center spacing (O.C.) is measured from the centre of one framing member to the centre of the next. Common layouts are 16 in (406 mm) and 24 in (610 mm). Stud and joist counts put one member at each end and one on every O.C. mark: ceil((length − 1.5 in) / O.C.) + 1, then extras for openings or beams. The convention stays 16/24 even when the wall length is shown in metres.

Calculators that use this

• Carpentry & framing

  Wall Framing Stud Estimator

  Estimate studs, extra jack/king pairs for openings, and triple-plate lumber for a wall of given length and on-center spacing.

• Carpentry & framing

  Deck Joist & Beam Span Calculator

  Estimate maximum joist span, joist count and whether a mid-span beam is needed from species, 2x size and spacing, based on the prescriptive deck joist span table.