Board Feet Calculator

What a board foot is

A board foot is a unit of volume, not of area or of length. One board foot is 144 cubic inches: a piece one inch thick, twelve inches wide and twelve inches long. Change any of those three and the others can move to match, so a piece one inch thick, six inches wide and twenty four inches long is also exactly one board foot.

The formula is thickness times width times length, all in inches, divided by 144. That is what this page runs on every row, then multiplies by the quantity and adds the rows together.

When a woodworker prices by the board foot

Hardwood is sold this way and sheet goods are not. Walnut, maple, white oak and cherry come off a rack as random widths and random lengths, so a yard cannot price them by the piece and quotes a rate per board foot instead. Plywood, MDF and melamine come in a fixed 2440 x 1220 mm sheet, so those are priced by the sheet and never turn up in this calculation.

In a cabinet shop that usually means the solid stock: door stiles and rails, face frames, drawer sides, a solid edge on a plywood shelf, a run of trim. You price those by the board foot and everything else by the sheet, which is why this tool takes a list of pieces rather than one piece. A door has four parts and a kitchen has a lot of doors.

A worked example

Say a door stile 3/4 in thick, 2 1/4 in wide and 30 in long. Multiply those together and you get 50.625 cubic inches. Divide by 144 and the stile is 0.35 board feet. Four of them, two stiles and two rails cut to the same section, comes to about 1.41 board feet, and at a rate of $8.50 the stock for that door is a little under twelve dollars before waste.

Enter the same numbers in whichever unit you actually work in. The dimension fields follow the unit picker, including fractional inches, and the board feet total comes out in board feet either way, because it is a pricing convention rather than a measurement system.

The nominal thickness option

Hardwood is usually sold at a nominal quarter thickness, written 4/4, 5/4, 6/4 and so on, and rounded up from the real thickness because a mill saws to that nominal size and planing takes some of it back off. Your finished 3/4 in stile was bought as 4/4 stock and you paid for the full inch. The checkbox below rounds each thickness up to the next quarter inch before the arithmetic runs, which is what a yard's invoice will look like. It is off by default, so an untouched calculation answers the question actually asked, which is how much wood is in the piece.