How to Calculate Board Feet (With Examples)
Hardwood is priced by the board foot (BF), a unit of volume, not length. Once you know the formula you can price any board in a few seconds.
What is a board foot?
One board foot is 144 cubic inches: a piece 1” thick, 12” wide and 12” long. A 2” × 6” × 12” piece is also one board foot, and so is a 1” × 4” × 36” piece.
The formula
Board feet = thickness (in) × width (in) × length (ft) ÷ 12
If all three measurements are in inches, divide by 144 instead:
Board feet = thickness × width × length (all in inches) ÷ 144
Worked examples
| Board | Math | Board feet |
|---|---|---|
| 4/4 × 6” × 8 ft | 1 × 6 × 8 ÷ 12 | 4.0 |
| 4/4 × 8” × 10 ft | 1 × 8 × 10 ÷ 12 | 6.67 |
| 8/4 × 7” × 9 ft | 2 × 7 × 9 ÷ 12 | 10.5 |
| 2x4 × 8 ft | 2 × 4 × 8 ÷ 12 | 5.33 |
| 2x10 × 12 ft | 2 × 10 × 12 ÷ 12 | 20.0 |
| 4x4 × 8 ft | 4 × 4 × 8 ÷ 12 | 10.67 |
Use nominal thickness, not actual
Board feet are calculated on the nominal (rough) size:
- Hardwood: 4/4 counts as 1” even though surfaced 4/4 is about 13/16” thick. See what 4/4, 5/4 and 8/4 mean.
- Dimensional lumber: a 2x4 counts as 2” × 4” even though it measures 1½” × 3½”.
Random-width hardwood
Hardwood dealers sell boards in random widths and lengths. For a stack of boards that share a thickness:
- Measure each board’s width and length.
- Calculate board feet per board, then add them up.
Some yards round widths to the nearest inch and lengths down to the nearest foot, so your number and the yard’s may differ slightly. Ask how they tally.
From board feet to cost
Cost = board feet × price per board foot
A 4/4 × 6” × 8 ft walnut board is 4 BF. At $14/BF it costs $56.
To compare a per-piece price with a per-BF price, divide by the board’s board feet. An 8 ft 2x4 (5.33 BF) selling for $8 works out to $1.50/BF.
Board feet vs. linear feet
A linear foot is just 12” of length, whatever the width or thickness. Trim, molding and deck boards are usually sold by the linear foot; hardwood by the board foot.
A 1x6 that is 8 ft long is 8 linear feet but only 4 board feet.
Add waste
You’ll never use 100% of a board. Knots, checks, end splits and grain matching all cost material. Plan to buy about:
- 10–15% extra for clear, surfaced stock
- 20–30% extra for rough lumber or common grades
- 35%+ if you’re matching grain or working with figured boards
Do it faster
The board foot calculator handles multiple boards, adds waste, prices the total by species, and gives you a printable cut list. For a full project example, see how much lumber you need for a table.