To calculate the board feet needed for a wood project, multiply width by length by thickness and divide by 144. All of the measurements should be in inches. For example, 8 inches by 72 inches by 1.5 inches divided by 144 equals 6 board feet.
If the length is in feet, use the following formula: width in inches times length in feet times thickness in inches divided by 12.
Because hardwoods come in different sizes, lumber yards use the board foot as a standard unit of measurement and pricing. In contrast, softwoods are cut to consistent sizes, known as dimensional lumber.