Board Foot Calculator
Enter one board size and how many you need. Use nominal or rough thickness (4/4 = 1 in).
Carpentry
Board Foot Calculator
Quick answer: board feet = thickness (in) × width (in) × length (ft) ÷ 12. A board 1 in thick, 6 in wide, and 8 ft long is 1 × 6 × 8 ÷ 12 = 4 board feet; ten of them are 40 BF, or $260 at $6.50 per board foot.
Find the board feet in any lumber order — rough hardwood in 4/4 to 16/4 thicknesses or dimensional softwood — plus linear feet, cubic volume, and cost from a price per board foot.
Board dimensions
How to calculate board feet
A board foot is a volume: a piece 1 in thick, 12 in wide, and 1 ft long, or 144 cubic inches. Hardwood dealers and sawmills sell by the board foot because boards come in random widths and lengths, so price per piece would not work.
T (in) × W (in) × L (ft) ÷ 12
= board feet per board; multiply by the number of boards
- Record thickness in inches. For rough hardwood use the quarter size: 4/4 = 1, 5/4 = 1.25, 6/4 = 1.5, 8/4 = 2.
- Measure width in inches at the narrowest usable point of a random-width board.
- Measure length in feet. If you measure in inches, divide the result by 144 instead of 12.
- Multiply and divide by 12 for board feet per board, then multiply by the count.
- Add extra for knots, checks, sapwood, and milling losses — commonly 15–30% for rough hardwood.
Worked example: walnut for a dining table
You need 12 boards of 8/4 walnut, each 7 in wide and 9 ft long, at $12 per board foot, plus 20% for defects.
- Per board: 2 × 7 × 9 ÷ 12 = 10.5 BF
- 12 boards: 10.5 × 12 = 126 BF (108 linear feet)
- With 20% extra: 126 × 1.2 = 151.2 BF
- Cost: 151.2 × $12 = $1,814
Board feet for common lumber sizes
Calculated on nominal dimensions, which is how lumber is tallied. Linear feet per board foot tells you how many feet of that size make one board foot.
| Nominal size | Board feet per piece | Linear ft per board foot |
|---|---|---|
| 1 × 4 × 8 ft | 2.67 | 3.00 |
| 1 × 6 × 8 ft | 4.00 | 2.00 |
| 1 × 8 × 10 ft | 6.67 | 1.50 |
| 1 × 12 × 8 ft | 8.00 | 1.00 |
| 2 × 4 × 8 ft | 5.33 | 1.50 |
| 2 × 6 × 10 ft | 10.00 | 1.00 |
| 2 × 8 × 12 ft | 16.00 | 0.75 |
| 2 × 10 × 12 ft | 20.00 | 0.60 |
| 2 × 12 × 16 ft | 32.00 | 0.50 |
| 4 × 4 × 8 ft | 10.67 | 0.75 |
| 6 × 6 × 8 ft | 24.00 | 0.33 |
Nominal vs. actual size
Board footage is figured on nominal dimensions, not the size you measure after planing. Softwood construction lumber shows the gap most clearly: a 2×4 is actually 1½ × 3½ in, a 2×6 is 1½ × 5½ in, and a 1× board is ¾ in thick, yet a 2×4×8 is still tallied as 5.33 board feet. Most home centers sell these by the piece or linear foot, but lumberyards quoting a large framing package may price by the thousand board feet (MBF).
Rough hardwood is sold by quarter-inch thickness: 4/4 (“four quarter”) is about 1 in thick rough, 5/4 is 1¼ in, 6/4 is 1½ in, and 8/4 is 2 in. You pay for that rough thickness even though surfacing removes material — 4/4 stock planed on both sides (S2S) typically finishes around 13/16 in, and 8/4 around 1¾ in. When you price surfaced hardwood, confirm whether the dealer tallies on the rough or finished size, and plan your cut list with the finished thickness.
Board foot tips and common mistakes
- Mixing inches and feet in length. The ÷ 12 formula needs length in feet. With all three dimensions in inches, divide by 144.
- Confusing board feet with linear feet. 10 linear feet of 1×6 is 5 board feet; 10 linear feet of 2×12 is 20 board feet.
- Buying exactly the cut list. Rough boards have defects, end checks, and twist. Add 15–30% for hardwood, more for figured or lower grades.
- Forgetting thickness loss. If you need a finished 1 in top, buy 5/4 rough, not 4/4.
- Assuming every yard measures the same way. Some round each board’s footage or measure width to the nearest inch. Ask how they tally before comparing prices.
Board foot FAQ
How do you calculate board feet?
Multiply thickness in inches by width in inches by length in feet, then divide by 12. A 2 × 6 that is 10 ft long is 2 × 6 × 10 ÷ 12 = 10 board feet. One board foot equals 144 cubic inches, such as a piece 1 in × 12 in × 12 in.
How many board feet are in a 2x4x8?
A 2×4×8 is 2 × 4 × 8 ÷ 12 = 5.33 board feet. Board footage uses the nominal size, even though the actual board measures 1½ × 3½ in. That means 100 studs of that size equal about 533 board feet.
What does 4/4 mean in lumber?
It is the hardwood thickness in quarters of an inch: 4/4 is about 1 in thick rough, 5/4 is 1¼ in, 6/4 is 1½ in, and 8/4 is 2 in. Board feet are figured on that rough thickness. After surfacing both faces, 4/4 typically ends up around 13/16 in thick.
How do you convert linear feet to board feet?
Multiply the linear feet by the thickness and width in inches, then divide by 12. For example, 100 linear feet of 1×6 is 100 × 1 × 6 ÷ 12 = 50 board feet. For 2×12 stock, the same 100 linear feet is 200 board feet.
How do you figure lumber cost by the board foot?
Multiply total board feet by the price per board foot. Forty board feet at $6.50 is $260. To compare with a per-foot price, multiply the board-foot price by thickness × width ÷ 12: a 1×6 at $6.50 per board foot costs $3.25 per linear foot.
Do you use actual or nominal size for board feet?
Lumber is tallied on nominal size, so a 2×4 counts as 2 × 4 in even though it measures 1½ × 3½ in. Rough hardwood is measured at its rough quarter thickness, such as 4/4 or 8/4. Only use actual dimensions when you want the true volume of wood you already have.
How we built this calculator: results use the standard volume, area, and coverage formulas shown on this page, with typical U.S. material densities, bag yields, and waste factors that you can override. Written and checked by the YardsCalculator editorial team. Last reviewed: October 2026.