OSB Sheathing Calculator

Enter your wall and roof area to find the number of OSB sheets needed.

How to use

  1. Enter your values in the fields above.
  2. Press Calculate to see your result instantly.
  3. Use the Share button to copy a link to your result.

About this calculator

Oriented strand board (OSB) sheathing comes in a standard 4×8 foot panel — 32 square feet of coverage per sheet — used per APA (The Engineered Wood Association) and IRC building-code guidance to sheathe exterior walls and roof decks in wood-frame construction. The base material need is simply total area ÷ 32, rounded up to whole sheets.

Real jobs need more than that raw count because of window and door cutouts, roof hips and valleys, and offcuts that can't be reused on the next section, so builders typically add a 10–15% waste allowance on top of the base calculation — the same margin lumber yards and framing crews use when ordering material for a job so they aren't caught short mid-build.

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