Board foot calculator
Total board feet for your lumber list, with cost if you know the price per board foot.
Your list comes to
93.33 board feet
- Before waste
- 93.33 bd ft
- Volume
- 7.78 cu ft
- Metric
- 0.220 m³
- Linear feet
- 120.0 ft
- Boards
- 14
- Estimated cost
Nominal sizes, including the waste you set. Volume and cost include waste; linear feet don't.
How to calculate board feet
A board foot is a volume of wood: 1 inch thick, 12 inches wide and 12 inches long, or 144 cubic inches. Hardwood and rough lumber are priced by the board foot, so it's how you compare prices across sizes.
- Board feet per board = thickness (in) × width (in) × length (ft) ÷ 12
- With length in inches: thickness × width × length ÷ 144
- Total = board feet per board × number of boards, added up for every line, plus your waste percentage
- Cubic feet = board feet ÷ 12
Worked example
6 boards of 2×6, each 10 ft long: 2 × 6 × 10 ÷ 12 = 10.00 board feet each. 10.00 × 6 = 60.00 board feet, or 5.00 cubic feet.
Nominal and actual lumber sizes
Board feet always use the nominal size, the name the lumber is sold under, not the smaller size it measures after drying and planing. Typical dry sizes per the American Softwood Lumber Standard (PS 20); individual mills vary slightly.
| Nominal | Actual size (in) | Board feet per linear foot | Board feet per 8 ft board |
|---|---|---|---|
| 1×4 | 3/4 × 3 1/2 | 0.33 | 2.67 |
| 1×6 | 3/4 × 5 1/2 | 0.50 | 4.00 |
| 1×8 | 3/4 × 7 1/4 | 0.67 | 5.33 |
| 1×12 | 3/4 × 11 1/4 | 1.00 | 8.00 |
| 2×4 | 1 1/2 × 3 1/2 | 0.67 | 5.33 |
| 2×6 | 1 1/2 × 5 1/2 | 1.00 | 8.00 |
| 2×8 | 1 1/2 × 7 1/4 | 1.33 | 10.67 |
| 2×10 | 1 1/2 × 9 1/4 | 1.67 | 13.33 |
| 2×12 | 1 1/2 × 11 1/4 | 2.00 | 16.00 |
| 4×4 | 3 1/2 × 3 1/2 | 1.33 | 10.67 |
| 6×6 | 5 1/2 × 5 1/2 | 3.00 | 24.00 |
Hardwood thickness in quarters
Hardwood is sold by thickness in quarter inches: 4/4 ("four quarter") is 1 inch rough. Planed (S2S) boards are thinner but are still sold and counted at the rough thickness. Surfaced sizes are typical; ask your supplier.
| Quarters | Rough (nominal) thickness | Typical surfaced thickness |
|---|---|---|
| 4/4 | 1 in | 13/16 in |
| 5/4 | 1 1/4 in | 1 1/16 in |
| 6/4 | 1 1/2 in | 1 5/16 in |
| 8/4 | 2 in | 1 3/4 in |
| 12/4 | 3 in | 2 3/4 in |
| 16/4 | 4 in | 3 3/4 in |
Board foot questions
What is a board foot?
A unit of lumber volume equal to a board 1 inch thick, 12 inches wide and 1 foot long: 144 cubic inches. It doesn't have to be that shape; a 2 × 6 that's 1 foot long is also 1 board foot. There are 12 board feet in a cubic foot.
Do I use the nominal or actual size?
The nominal size. A 2×4 measures about 1 1/2 × 3 1/2 inches, but it's counted as 2 × 4 when figuring board feet. Hardwood works the same way: 4/4 lumber is counted as 1 inch thick even after planing.
How many board feet are in a 2×4?
A 2×4 has 0.67 board feet per linear foot, so a 2×4×8 is 5.33 board feet and a 2×4×10 is 6.67. Linear feet measure length only; board feet include thickness and width. The table above lists other common sizes.
How do I convert board feet to square feet?
Divide board feet by the thickness in inches. For 1-inch (4/4) lumber, 1 board foot covers 1 square foot. For 2-inch lumber, 100 board feet covers 50 square feet. This is the face area of the boards, before gaps or waste.
How much is a board foot?
It depends on the species and grade, so ask your supplier. To compare a store's price per board with a price per board foot, divide the board's price by its board feet: an 8 ft 2×6 holds 8.00 board feet, so at $12.00 a board you're paying $1.50 per board foot.
How much extra lumber should I buy?
For framing with straight, graded lumber, 5 to 10% usually covers cutting loss and a bad board or two. For rough hardwood, plan on 15 to 30%, because knots, splits and planing take more. Enter it as the waste percentage above.