Board Foot Calculator
Work out board feet, cubic feet and cubic metres for one board or a whole list, with linear feet, waste and what the lumber will cost.
Fractions are fine: 3/4, 1 1/2 or 1½. In quarters, type 8 (or 8/4) for 2 in.
Only changes boards picked from the lumber sizes. Yards usually price dimensional lumber on the nominal size.
Rule of thumb: 10–15% for framing, 20–30% for rough hardwood.
Typical dry weights; wet or green wood is much heavier.
Type the length of the boards you'll buy and the pieces you need. Pieces are packed longest first, with a saw cut between each.
A typical saw blade takes about 1/8 in (3 mm).
How your board feet are worked out
Thickness (in) × width (in) × length (ft) ÷ 12, then times how many boards.
- 1
Thickness × width
1 in × 6 in= 6 sq in
- 2
Times the length
6 × 8 ft= 48
- 3
Divide by 12
48 ÷ 12= 4 bd ft each
- 4
Times how many
4 × 10 boards= 40 bd ft
Read more: the formula, a worked example, nominal and actual sizes, quarters and tips
A board foot is a unit of wood volume: a piece 1 in thick, 12 in wide and 1 ft long, which is 144 cubic inches. Lumber yards in the United States and Canada sell hardwood, and often softwood, by the board foot. Elsewhere timber is usually sold by the cubic metre or by the linear metre, so the calculator shows all of them.
The formula
board feet = thickness in inches × width in inches × length in feet ÷ 12 × how many boards
(or thickness × width × length, all in inches, ÷ 144)
quarters: 4/4 = 1 in, 5/4 = 1¼ in, 8/4 = 2 in (n/4 inches)
cubic feet = board feet ÷ 12
cubic metres = board feet × 0.002359737 (1 m³ ≈ 423.78 board feet)
linear feet = length in feet × how many boards
to buy = each amount × (1 + waste % ÷ 100)
cost = price × amount in the price's unit; the other prices = cost ÷ that amount
weight = cubic metres × wood density in kg/m³
Worked example
Ten boards, each 1 in thick, 6 in wide and 8 ft long. One board is 1 × 6 × 8 ÷ 12 = 48 ÷ 12 = 4 board feet, so ten are 4 × 10 = 40 board feet. That is 40 ÷ 12 = 3.33 cubic feet, or 40 × 0.002359737 = 0.0944 m³. The length is 8 × 10 = 80 linear feet (24.38 m). At 5 per board foot the wood costs 40 × 5 = 200, which is 200 ÷ 80 = 2.50 per linear foot or 200 ÷ 0.0944 = about 2,119 per m³.
A 2×4 that is 8 ft long counts as 2 × 4 × 8 ÷ 12 = 5.33 board feet on its name size, but the real wood (1½ × 3½ in) is 1.5 × 3.5 × 8 ÷ 12 = 3.5 board feet.
Nominal and actual sizes (typical)
| Called | Actual, typical | Bd ft per ft, nominal | Bd ft per ft, actual |
|---|---|---|---|
| 1×2 | ¾ × 1½ in (19 × 38 mm) | 0.167 | 0.094 |
| 1×3 | ¾ × 2½ in (19 × 64 mm) | 0.25 | 0.156 |
| 1×4 | ¾ × 3½ in (19 × 89 mm) | 0.333 | 0.219 |
| 1×6 | ¾ × 5½ in (19 × 140 mm) | 0.5 | 0.344 |
| 1×8 | ¾ × 7¼ in (19 × 184 mm) | 0.667 | 0.453 |
| 1×10 | ¾ × 9¼ in (19 × 235 mm) | 0.833 | 0.578 |
| 1×12 | ¾ × 11¼ in (19 × 286 mm) | 1 | 0.703 |
| 2×2 | 1½ × 1½ in (38 × 38 mm) | 0.333 | 0.188 |
| 2×3 | 1½ × 2½ in (38 × 64 mm) | 0.5 | 0.313 |
| 2×4 | 1½ × 3½ in (38 × 89 mm) | 0.667 | 0.438 |
| 2×6 | 1½ × 5½ in (38 × 140 mm) | 1 | 0.688 |
| 2×8 | 1½ × 7¼ in (38 × 184 mm) | 1.333 | 0.906 |
| 2×10 | 1½ × 9¼ in (38 × 235 mm) | 1.667 | 1.156 |
| 2×12 | 1½ × 11¼ in (38 × 286 mm) | 2 | 1.406 |
| 4×4 | 3½ × 3½ in (89 × 89 mm) | 1.333 | 1.021 |
| 4×6 | 3½ × 5½ in (89 × 140 mm) | 2 | 1.604 |
| 6×6 | 5½ × 5½ in (140 × 140 mm) | 3 | 2.521 |
Typical dry, planed (S4S) sizes for softwood dimensional lumber in North America: 1 in nominal is ¾ in, 2–6 in lose ½ in, and 8 in and wider lose ¾ in. Green, rough-sawn and imported timber can be different, so measure if it matters. Metric timber is usually sold by its real size in mm.
Hardwood thickness in quarters
| Quarters | Rough thickness | Bd ft per sq ft of board |
|---|---|---|
| 4/4 | 1 in (25 mm) | 1 |
| 5/4 | 1¼ in (32 mm) | 1.25 |
| 6/4 | 1½ in (38 mm) | 1.5 |
| 8/4 | 2 in (51 mm) | 2 |
| 10/4 | 2½ in (64 mm) | 2.5 |
| 12/4 | 3 in (76 mm) | 3 |
| 16/4 | 4 in (102 mm) | 4 |
Rough hardwood is counted at its rough thickness. A board bought planed to a smaller thickness is still usually sold at the quarter size, so enter the quarter size to match the yard's bill.
Tips
- Some hardwood yards round each board's width up to the next whole inch and measure length in whole feet, so their total can be a little higher than yours.
- Board feet are a volume, so a wide thin board and a narrow thick one can be the same price.
- Use the cut list to see how many stock boards you need; then press "Put these boards in Board 1" to price them.
- Wood weights are typical air-dry figures (about 12% moisture). Freshly sawn wood can weigh half as much again.
Common questions
How do you calculate board feet?
Multiply the thickness in inches by the width in inches and the length in feet, then divide by 12. A board 1 in thick, 6 in wide and 8 ft long is 1 × 6 × 8 ÷ 12 = 4 board feet. Ten of them make 40 board feet. One board foot is a piece 1 in thick, 12 in wide and 1 ft long (144 cubic inches).
How many board feet are in a 2×4×8?
Lumber yards count a 2×4 by its name size, so a 2×4 that is 8 ft long is 2 × 4 × 8 ÷ 12 = 5.33 board feet. The wood itself is smaller: a typical dry 2×4 is 1½ × 3½ in, which is 1.5 × 3.5 × 8 ÷ 12 = 3.5 board feet of real wood. Advanced lets you pick either.
What do 4/4, 5/4 and 8/4 mean?
Hardwood thickness is often given in quarters of an inch. 4/4 ("four quarter") is 1 in, 5/4 is 1¼ in, 6/4 is 1½ in and 8/4 is 2 in, measured on the rough board. Planed boards end up thinner but are usually still sold and counted at the quarter size. Pick quarters as the thickness unit and type 4, 5, 6 or 8.
How do I convert board feet to cubic metres or cubic feet?
One board foot is 144 cubic inches, so 12 board feet make 1 cubic foot. In metric, 1 board foot is 0.00236 m³ and 1 m³ is about 423.8 board feet. So 40 board feet is 3.33 cubic feet or 0.0944 m³. The calculator shows all three at once.
What is the difference between board feet and linear feet?
Linear feet only count length, whatever the size of the board. Board feet count volume, so they take the thickness and width into account. A 1×6 board 8 ft long is 8 linear feet but 4 board feet. Many yards price boards by the linear foot and hardwood by the board foot; the calculator turns one price into the other.
How much extra lumber should I buy for waste?
As a rule of thumb, add about 10–15% for framing and simple projects, and 20–30% for rough hardwood that you will plane, rip and cut around knots and splits. Add it in Advanced and the board feet, volume, length, pieces and cost all include it.
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