A board foot is 144 cubic inches of wood: a piece 1 inch thick, 12 inches wide and 1 foot long. To find the board feet in a board, multiply thickness in inches by width in inches by length in feet and divide by 12. A 4/4 board 6 inches wide and 8 feet long holds 4 board feet; ten of them hold 40.
How the board feet are calculated
Board feet = thickness (in) × width (in) × length (ft) ÷ 12 × pieces
The division by 12 turns the inch × inch × foot product into the 144 cubic inch unit. The American Softwood Lumber Standard (PS 20-25, section 2.2) defines board measure the same way, with the width taken in feet: nominal thickness in inches × nominal width in feet × length in feet. The American Hardwood Export Council writes it as width × length × thickness ÷ 12.
The calculator adds every row, then shows the total in board feet, cubic feet (board feet ÷ 12) and cubic meters. In metric mode it measures in centimeters and meters and divides the volume by 2,359.7 cm³, the metric size of one board foot.
Worked example: a hardwood order
You are buying for a table: ten boards of 4/4 cherry, 6 inches wide and 8 feet long, and two 8/4 boards, 8 inches wide and 10 feet long, for the legs.
- 4/4 boards: 1 × 6 × 8 ÷ 12 = 4 board feet each, 40 board feet for ten.
- 8/4 boards: 2 × 8 × 10 ÷ 12 = 13.33 board feet each, 26.67 board feet for two.
- Total: 66.67 board feet, about 5.56 cubic feet.
At $4.50 per board foot for the 4/4 and $7.25 for the 8/4, the order costs $180.00 + $193.33 = $373.33. Those are the calculator's default rows; type the two prices into the price fields to see the same figures.
Board foot calculator for lumber: quarters, nominal sizes and actual sizes
Hardwood is sold by the quarter inch of rough thickness: 4/4 is 1 inch, 5/4 is 1¼ inches, 8/4 is 2 inches. You pay for the rough thickness even though the board shrinks when it is planed. AHEC gives the surfaced (S2S) thickness as the rough size minus 3/16 inch up to 1½ inches, and minus ¼ inch from 1¾ inches, so 4/4 planes to 13/16 inch and 8/4 to 1¾ inches. AHEC also notes that random widths are tallied to the nearest whole inch and lengths are rounded down to the whole foot, so a 5¼ inch by 8½ foot board is tallied as 5 inches by 8 feet.
Softwood dimension lumber is tallied on its nominal size. A 2x4 is 1½ × 3½ inches dry (PS 20-25, Table 3), but it counts as 2 × 4 when you figure board feet. Pick a nominal size in the row and the calculator uses the nominal numbers and prints the dressed size under the field.
| Nominal | Actual (dry) | Nominal | Actual (dry) |
|---|---|---|---|
| 1x4 | ¾ × 3½ in | 2x4 | 1½ × 3½ in |
| 1x6 | ¾ × 5½ in | 2x6 | 1½ × 5½ in |
| 1x8 | ¾ × 7¼ in | 2x8 | 1½ × 7¼ in |
| 1x10 | ¾ × 9¼ in | 2x10 | 1½ × 9¼ in |
| 1x12 | ¾ × 11¼ in | 2x12 | 1½ × 11¼ in |
Sizes are the minimum dressed dry sizes of PS 20-25, Table 3. Timbers 5 inches and thicker lose ½ inch each way, so a 6x6 is 5½ × 5½ inches.
Board foot chart for common sizes
Board feet per piece, nominal size × length:
| Size | Per linear ft | 8 ft | 10 ft | 12 ft | 16 ft |
|---|---|---|---|---|---|
| 1x4 | 0.33 | 2.67 | 3.33 | 4 | 5.33 |
| 1x6 | 0.5 | 4 | 5 | 6 | 8 |
| 1x8 | 0.67 | 5.33 | 6.67 | 8 | 10.67 |
| 1x12 | 1 | 8 | 10 | 12 | 16 |
| 2x4 | 0.67 | 5.33 | 6.67 | 8 | 10.67 |
| 2x6 | 1 | 8 | 10 | 12 | 16 |
| 2x8 | 1.33 | 10.67 | 13.33 | 16 | 21.33 |
| 2x10 | 1.67 | 13.33 | 16.67 | 20 | 26.67 |
| 2x12 | 2 | 16 | 20 | 24 | 32 |
| 4x4 | 1.33 | 10.67 | 13.33 | 16 | 21.33 |
| 6x6 | 3 | 24 | 30 | 36 | 48 |
Board foot price
Hardwood dealers quote a price per board foot, sometimes per thousand board feet (MBF): $4,500 per MBF is $4.50 per board foot. Enter a price in each row to get the cost of that row and of the whole order. Rows without a price are left out of the cost, and the answer tells you when that happens. Dimension lumber at a home center is priced per piece; divide the piece price by its board feet from the chart to compare it with a sawmill's quote.
How much wood to buy for a project
Board feet measure what you pay for, not what ends up in the furniture. Planing, ripping to width and crosscutting away checks at the ends all cost wood, so woodworkers buy extra over the finished volume of their parts; how much depends on the stock and the cut list. For framing and deck lumber, count pieces instead: the lumber calculator turns a list of cuts into 8 to 16 foot boards with the least waste and also totals the board feet.
What to work out next
- Buying logs or selling standing timber: the log board foot calculator scales a log by the Doyle, Scribner and International ¼ inch rules.
- Cabinet or shop projects in sheet goods: the plywood calculator lays out a cut list on 4 × 8 sheets.
- Building a deck: the deck board calculator counts boards and screws for the surface.
- Framing a wall: the framing calculator lists studs, plates and headers.
More tools for wood and sheet stock are collected under framing and lumber.