The Woodwork Bench / Field notes & guides
Wood calculator: board feet, waste and shopping quantities
Use this calculator to estimate the rough volume of rectangular timber. It is a planning aid, not a substitute for a cutting diagram: knots, grain direction, saw kerf and stock lengths all affect the quantity you actually need.
What a board foot means
One board foot is a volume of 144 cubic inches. For dimensions measured in inches, board feet = thickness × width × length ÷ 144. Enter the number of identical pieces and add a waste allowance.
For example, four pieces each 1 inch thick, 6 inches wide and 36 inches long require 4 × 1 × 6 × 36 ÷ 144 = 6 board feet before waste. A 15% allowance raises the estimate to 6.9 board feet.
Use the right units
The calculator below uses inches throughout. If your timber yard sells by cubic metre or by linear metre, convert the result or build a separate stock-length list. Do not mix millimetres and inches in the same calculation.
A board-foot estimate is not a shopping list
The volume calculation is useful for comparing quantities of rough timber, but it does not tell you how many merchant-length boards to buy. For example, four 36-inch parts might fit into two 8-foot boards if grain direction, defects, kerf and trimming allow. They will not fit into one 8-foot board. Draw a cutting layout using the stock lengths actually available before ordering.
Converting the result
One board foot equals 144 cubic inches, approximately 0.00236 cubic metres. A 6-board-foot estimate is approximately 0.0142 cubic metres before waste. Use this conversion only for volume: it does not convert the estimate into a number of boards, and sheet material is often sold by area or sheet size instead.
Troubleshooting the estimate
If the result seems implausible, check whether you entered finished inches rather than millimetres and whether the quantity is the number of identical parts. Waste is applied as a percentage of the calculated volume, not as a guarantee of enough usable stock. Knots, short offcuts and grain orientation can require more material than a simple percentage suggests.