Board Foot Calculator
Find the board feet (bd ft or BF) in a lumber order, and what it costs at a price per board foot. Enter the size, length, and quantity of each board. US sizes such as 2 × 4 count board feet from the nominal size, the way lumber is priced, and the calculator also gives the volume from the actual size.
- Choose US or Metric. You can still change the unit of any single field.
- Pick a Size for the first board. US sizes are nominal, with the actual size in parentheses. For hardwood boards or any other size, choose Custom size and enter the Thickness and Width.
- Enter the Length and the Quantity of boards with that size and length. Use Add board for each other size or length.
- Optionally, enter a Price per board foot (in Metric, a Price per m³) to estimate the cost.
The Thickness, Width, and Length fields accept whole numbers, decimals,
fractions, and mixed numbers, such as 6, 7.5, 5/4, or
7 1/2. Choose ft + in as the length unit to
enter a length such as 9 ft 6 in in two fields.
How to calculate board feet
A board foot is 144 cubic inches of wood, the same as a board 12 in wide, 12 in long, and 1 in thick. To find the board feet in a board:
Board feet = thickness (in) × width (in) × length (ft) ÷ 12
An 8 ft 2 × 4 is 2 × 4 × 8 ÷ 12 = 5.33 board feet, so ten of them are 53.33. The calculator adds up the board feet of every row and multiplies the total by the price:
Cost = total board feet × price per board foot
This is the board measure in PS 20-20, the American Softwood Lumber Standard published by NIST, and the same formula the American Hardwood Export Council (AHEC) gives for hardwood lumber. Board feet are rounded to 0.01 for display, and the cost is figured from the unrounded total.
Nominal and actual sizes
A 2 × 4 is named by its nominal size, but a dry 2 × 4 is only 1 1/2 × 3 1/2 in. PS 20-20 counts board feet from the nominal size, and lumber prices per board foot follow it, so the calculator does too. Counted from the actual size, an 8 ft 2 × 4 would be 1 1/2 × 3 1/2 × 8 ÷ 12 = 3.50 board feet instead of 5.33, about 34% less, and the cost would come out low. A 1x board counts as 1 in thick, though it's 3/4 in.
The Volume in the results uses the actual sizes, so it's the real amount of wood. PS 20-20 also figures cubic meters from the dressed (actual) size.
| Nominal | Actual (dry) | Bd ft per ft |
|---|---|---|
| 1 × 2 | 3/4 × 1 1/2 in | 0.17 |
| 1 × 3 | 3/4 × 2 1/2 in | 0.25 |
| 1 × 4 | 3/4 × 3 1/2 in | 0.33 |
| 1 × 6 | 3/4 × 5 1/2 in | 0.50 |
| 1 × 8 | 3/4 × 7 1/4 in | 0.67 |
| 1 × 10 | 3/4 × 9 1/4 in | 0.83 |
| 1 × 12 | 3/4 × 11 1/4 in | 1.00 |
| 2 × 2 | 1 1/2 × 1 1/2 in | 0.33 |
| 2 × 3 | 1 1/2 × 2 1/2 in | 0.50 |
| 2 × 4 | 1 1/2 × 3 1/2 in | 0.67 |
| 2 × 6 | 1 1/2 × 5 1/2 in | 1.00 |
| 2 × 8 | 1 1/2 × 7 1/4 in | 1.33 |
| 2 × 10 | 1 1/2 × 9 1/4 in | 1.67 |
| 2 × 12 | 1 1/2 × 11 1/4 in | 2.00 |
| 4 × 4 | 3 1/2 × 3 1/2 in | 1.33 |
| 4 × 6 | 3 1/2 × 5 1/2 in | 2.00 |
| 6 × 6 | 5 1/2 × 5 1/2 in | 3.00 |
The actual sizes are the minimum dry sizes in PS 20-20 Table 3. A 6 × 6 timber is 1/2 in under nominal both ways. Check the size on the label of your lumber.
Hardwood and custom sizes
Hardwood lumber is sold by the board foot, with the thickness in quarters
of an inch: 4/4 is 1 in, 5/4 is 1 1/4 in, and 8/4 is 2 in. Choose
Custom size and enter the thickness as written, such as
5/4, with the width you measure on each board. A custom size
uses the numbers you enter for both the board feet and the volume.
AHEC puts the finished thickness of surfaced lumber 1 1/2 in and thinner at 3/16 in under nominal, so a surfaced 4/4 board is about 13/16 in. To compare with a lumberyard's board feet, enter the nominal 4/4. A 4/4 × 7 1/2 in board 9 ft 6 in long is 5.94 board feet. Entered at 13/16 in, it comes out at 4.82, about 19% less.
A bill can differ a little from the calculator. Some hardwood dealers round each board's surface measure (width in inches × length in feet ÷ 12) to a whole number before multiplying by the thickness. In AHEC's example, a 2 in × 6 1/4 in board 8 ft long is billed as 8 board feet, while the calculator gives 8.33. And lumber tallied before kiln drying (a green tally) shrinks in the kiln: AHEC says to expect about 7% fewer board feet when you buy kiln-dried lumber by the green tally. The calculator counts the sizes you enter.
Metric lumber
In Metric, the sizes are actual sizes, such as 38 × 89 mm, and the result is the volume in m³, with ft³ below it. The calculator doesn't give board feet in Metric, because board feet are counted from US nominal sizes: a 38 × 89 mm board 2.4 m long would be about 3.44 board feet from its actual size, while the US 2 × 4 × 8 ft counts 5.33. If your lumber is sold as a 2 × 4, such as Canadian 38 × 89 mm studs, switch to US and choose 2 × 4.
Volume (m³) = thickness (m) × width (m) × length (m)
The volume is shown to 0.001 m³, which is 1 liter. For the cost, enter a Price per m³. In the UK, The English Woodworker notes that European timber is often priced per cubic meter and American timber per cubic foot. Multiply a price per ft³ by 35.315 to get the price per m³.
Examples
Framing lumber and hardwood
Ten 2 × 4s 8 ft long are 53.33 board feet. Four 5/4 × 6 in hardwood boards 8 ft long add 1 1/4 × 6 × 8 ÷ 12 × 4 = 20.00, for 73.33 board feet and a volume of 4.583 ft³ (0.130 m³) from the actual sizes. At $4.50 per board foot, the cost is $330.00.
Posts, timbers, and joists
An 8 ft 4 × 4 is 10.67 board feet, a 10 ft 6 × 6 is 30.00, and a 16 ft 2 × 12 is 32.00.
A Metric order
Ten 38 × 89 mm boards 2.4 m long and four 25 × 150 mm boards 3 m long are 0.081 + 0.045 = 0.126 m³ (4.456 ft³). At £650 per m³, the cost is £82.01.
FAQ
Multiply the thickness in inches by the width in inches and the length in feet, then divide by 12. A 1 × 6 board 8 ft long is 1 × 6 × 8 ÷ 12 = 4 board feet.
5.33 in an 8 ft 2 × 4, counted from its nominal size. Each foot of 2 × 4 is 2 × 4 ÷ 12 = 0.67 board feet, so a 10 ft 2 × 4 is 6.67 and a 12 ft 2 × 4 is 8.00.
The nominal size, for softwood lumber such as 2 × 4s: PS 20-20 counts board feet from the nominal thickness and width. For hardwood, enter the nominal thickness in quarters, such as 4/4, and the width you measure.
12. A cubic foot is 1,728 cubic inches and a board foot is 144, so 1,728 ÷ 144 = 12 for solid wood. Lumber counted from nominal sizes has more: a cubic foot of actual 2 × 4s is about 18 board feet.
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