Board Foot Calculator

In short A board foot is a VOLUME, not an area: exactly 144 cubic inches, which is a piece one foot square and one inch thick. That definition is the whole tool, and it is why two boards of completely different shapes can be the same board footage — a 1 × 12 twelve inches long and a 2 × 6 twelve inches long are both exactly one board foot. The arithmetic is thickness × width × length in inches, divided by 144, and because 144 is a definition rather than a measurement, board feet divided by cubic inches always comes out at the same number no matter what board you put in. Two things trip people up. Rough hardwood is sold in QUARTERS of an inch — 4/4 is one inch, 5/4 is an inch and a quarter, 8/4 is two — and that number is the thickness before planing, so a 4/4 board measures a full inch when you buy it and about seven eighths once it is surfaced. And hardwood is normally priced on its rough dimensions, so entering the dressed thickness will under-count what you are actually paying for. Softwood is different again: it is sold by nominal size, where a 2 × 4 is neither 2 nor 4. See /lumber-size-chart/ for that.