Board Foot Calculator
Enter each board's thickness, width, length, and quantity. Board feet and cost update as you type. Add a price per board foot to estimate what the lumber will cost.
| Thickness (in) | Width (in) | Length | Qty | $/bd ft | Bd ft |
|---|
Thickness tip: hardwood quarters run 4/4 = 1″, 5/4 = 1.25″, 6/4 = 1.5″, 8/4 = 2″. Price is optional.
How to calculate board feet
A board foot is a volume of wood equal to a piece 1″ thick × 12″ wide × 1′ long. To calculate it, multiply the three dimensions of your board and divide by the right constant:
If you measured the length in inches instead of feet, divide by 144:
Multiply by the number of identical boards, then repeat for every size in your cut list and add the results. That running total is what this calculator does for you.
What is a board foot?
A board foot (abbreviated bd ft or BF; sometimes FBM, for "foot, board measure") is the standard unit for buying and selling hardwood lumber in North America. It measures volume, not length: one board foot is 144 cubic inches of wood, in any shape. A 1×12 that's 1′ long and a 4×4 that's 9″ long are both one board foot.
Lumberyards price rough hardwood by the board foot because boards come in random widths and lengths. Two stacks of walnut can look completely different but cost the same if they contain the same volume of wood.
Nominal vs. actual dimensions
Board feet are figured from nominal (rough) dimensions, the size of the board before it was surfaced smooth. A surfaced "2×4" measures 1.5″ × 3.5″ once surfaced, but its board footage is still based on 2 × 4. The same goes for hardwood quarters: 4/4 stock surfaced to 13/16″ still sells as 1″ thick.
| Nominal size | Actual size (surfaced) | Bd ft per 8′ board |
|---|---|---|
| 1 × 4 | 0.75″ × 3.5″ | 2.67 |
| 1 × 6 | 0.75″ × 5.5″ | 4.00 |
| 1 × 8 | 0.75″ × 7.25″ | 5.33 |
| 1 × 12 | 0.75″ × 11.25″ | 8.00 |
| 2 × 4 | 1.5″ × 3.5″ | 5.33 |
| 2 × 6 | 1.5″ × 5.5″ | 8.00 |
| 2 × 8 | 1.5″ × 7.25″ | 10.67 |
| 2 × 12 | 1.5″ × 11.25″ | 16.00 |
| 4 × 4 | 3.5″ × 3.5″ | 10.67 |
Hardwood thickness in quarters
Hardwood dealers quote thickness in quarters of an inch, counted before surfacing:
| Quarter size | Rough thickness | Typical surfaced thickness |
|---|---|---|
| 4/4 ("four quarter") | 1″ | 13/16″ |
| 5/4 | 1.25″ | 1-1/16″ |
| 6/4 | 1.5″ | 1-5/16″ |
| 8/4 | 2″ | 1-3/4″ |
| 12/4 | 3″ | 2-3/4″ |
Frequently asked questions
How many board feet are in a 2×4×8?
Using nominal dimensions: 2 × 4 × 8 ÷ 12 = 5.33 board feet. An 8-foot 2×6 is exactly 8 board feet, which makes it an easy sanity check to remember.
Do I measure length in feet or inches?
Either works, just match the formula. With length in feet, divide by 12. With length in inches, divide by 144. This calculator lets you pick the unit per row.
What's the difference between a board foot and a linear foot?
A linear foot only measures how long the board is. A board foot measures volume: thickness × width × length. Ten linear feet of 1×2 is a lot less wood than ten linear feet of 2×12, but they're the same linear footage.
Should I buy extra beyond the calculated board feet?
Yes. Most woodworkers add 15–30% over the cut-list total to cover defects, checking, milling waste, and mistakes. Rough lumber especially: you lose wood flattening and squaring every board.
How much does a board foot cost?
Price depends mostly on species and grade, and on where you buy. Common affordable domestics include red oak and poplar. Walnut and cherry cost more, and exotics can cost several times as much. Your local hardwood dealer's price list is the real answer: enter their price in the calculator's $/bd ft column to estimate your project's cost.