Lumber math

How to Calculate Board Feet

Multiply thickness in inches by width in inches and length in feet, divide by 12, then multiply by quantity.

That is the board-foot calculation for a group of matching boards: thickness × width × length ÷ 12 × quantity. It works for one board or a complete material list, provided you calculate every different size as its own row.

Use the board foot calculator when your list has several sizes or mixed metric and imperial measurements.

1. Record the dimensions

Write down thickness and width in inches, length in feet, and the number of boards. For example, a pile of eight boards that are 1 inch thick, 8 inches wide, and 10 feet long has four inputs: 1, 8, 10, and 8.

2. Calculate one board

For one 1 in × 8 in × 10 ft board: 1 × 8 × 10 ÷ 12 = 6.667 board feet. Keep the decimal while you work instead of rounding each board to a whole number.

3. Multiply by the quantity

For eight matching boards: 6.667 × 8 = 53.333 board feet. If your list also has a different size, start a new calculation for that size and add the resulting totals at the end.

4. Check what dimensions the seller uses

Nominal dimensions and actual measurements are not always the same. Use the dimension basis shown on the seller's quote. If the seller quotes by actual surfaced size, calculate from that actual size; if the product is priced by nominal size, use the nominal dimensions.

A simple cut-list workflow

  1. Group matching lumber pieces on your list.
  2. Calculate board feet for one group at a time.
  3. Add all group totals before comparing prices.
  4. Keep any extra allowance for defects, kerf, or layout changes separate from the calculated order volume.

This approach makes it easier to spot a missing dimension or a quantity entered twice. It also prevents a single large board from being hidden inside an average size.

Questions about calculating board feet

How do I calculate board feet for several sizes?

Calculate every size on its own row, including its quantity, then add the row totals. The calculator does this automatically.

Can I use a decimal length?

Yes. Enter the length in decimal feet, or choose metres in the calculator and enter the metric value.

Should I round board feet?

Keep decimals while calculating. Your seller may have its own rounding or tally method, so use its stated billing rules for the final purchase amount.