Board Foot Calculator
This board foot calculator works out the board feet in a piece of lumber, or a stack of identical pieces, from its thickness, width and length. A board foot is a volume of 144 cubic inches, the same as a board 1 inch thick, 12 inches wide and 12 inches long, and it is how most hardwood and a lot of rough lumber is priced.
Pick a hardwood thickness such as 4/4 or 8/4 or type any thickness, enter the width and the length in feet or inches, and add a quantity. If you enter the price per board foot your lumber yard charges, it estimates the cost. It also shows cubic meters and linear feet, and accepts metric sizes in millimeters and meters.
Board Foot Calculator
How to Use the Board Foot Calculator
- 1
Choose units
Pick US (inches and feet) or Metric (millimeters and meters).
- 2
Enter the thickness
In US mode, pick a quarter thickness such as 4/4 or 8/4, or choose Custom and type the thickness in inches. In metric, type it in millimeters.
- 3
Enter the width and length
Type the width in inches (or mm) and the length, choosing feet or inches for the length in US mode.
- 4
Add quantity and price
Enter how many identical boards you have and, optionally, the price per board foot (or per cubic meter in metric).
- 5
Read the results
See the total board feet, board feet per piece, cubic meters, linear feet and the estimated cost.
How the board foot calculator works
Board feet is thickness in inches times width in inches times length in feet, divided by 12. Dividing by 12 converts the result into units of 144 cubic inches. If you enter the length in inches, the calculator divides it by 12 first. Metric sizes are converted to inches and feet (25.4 mm per inch, 0.3048 m per foot) before the same formula is applied.
The per-piece figure is multiplied by the quantity. Cubic meters use 1 board foot = 0.00236 m³, so 1 m³ is about 423.8 board feet. Cost is total board feet times price per board foot, or cubic meters times price per cubic meter in metric mode.
Board feet = thickness (in) × width (in) × length (ft) ÷ 12
Board feet = thickness (in) × width (in) × length (in) ÷ 144
Total = board feet per piece × quantity
1 board foot = 144 cu in ≈ 0.00236 m³Worked examples
- One 4/4 board, 6 in wide and 8 ft long: 1 x 6 x 8 ÷ 12 = 4 board feet.
- Five 8/4 boards, 8 in wide and 10 ft long: 2 x 8 x 10 ÷ 12 = 13.33 BF each, so 66.67 BF in total, or 0.157 m³.
- At an example price of $10 per board foot, those five boards would cost about $666.67. Prices vary widely by species, grade and region.
- A metric board 25 mm thick, 150 mm wide and 2.4 m long is 0.009 m³, or 3.81 board feet.
Board feet for common lumber sizes
Dimensional softwood is billed on its nominal size, so these figures use nominal inches, not the actual planed size.
| Nominal size | Length | Board feet per piece |
|---|---|---|
| 1 x 6 | 8 ft | 4 |
| 1 x 12 | 10 ft | 10 |
| 2 x 4 | 8 ft | 5.33 |
| 2 x 6 | 12 ft | 12 |
| 4 x 4 | 8 ft | 10.67 |
| 8/4 x 8 | 10 ft | 13.33 |
Nominal vs actual thickness in hardwood
Hardwood is sold by its rough thickness in quarters of an inch. A 4/4 ("four quarter") board is 1 inch thick rough, and 8/4 is 2 inches. When the yard surfaces it, the board gets thinner, but board feet are still usually calculated on the rough, nominal thickness. The table shows typical surfaced-two-sides (S2S) thicknesses under the common hardwood grading standard.
| Quarter | Rough (billed) thickness | Typical S2S 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 |
Tips and common mistakes
- Use the rough, nominal thickness (the quarter size) when checking a hardwood invoice, not the thickness you measure after planing.
- Hardwood is often sold in random widths and lengths. Measure each board and add them up, or group boards of the same size and use the quantity field.
- Buy extra for defects and offcuts. Many woodworkers add 20 to 30% or more for knots, checks and cutting waste on furniture projects.
- Do not confuse board feet with linear feet. Linear feet ignore thickness and width, so a 2 x 12 and a 1 x 2 of the same length have the same linear feet but very different board feet.
- Board feet measure volume only. For joists, beams, deck framing and other structural parts, size the lumber with the span tables in your local building code or ask an engineer.
Features
- Hardwood quarter thicknesses (4/4 to 16/4) or a custom thickness
- Length in feet or inches
- Quantity for multiple identical boards
- Optional price per board foot for a cost estimate
- Shows cubic meters and linear feet
- Metric input in millimeters and meters
Frequently Asked Questions
How do you calculate board feet?
Multiply the thickness in inches by the width in inches by the length in feet, then divide by 12. A board 1 inch thick, 6 inches wide and 8 feet long is 1 x 6 x 8 ÷ 12 = 4 board feet. If you measure the length in inches, divide by 144 instead of 12. Multiply by the number of boards for the total.
How many board feet are in a 2x4x8?
A 2x4 that is 8 feet long has 5.33 board feet: 2 x 4 x 8 ÷ 12 = 5.33. Lumber yards calculate board feet on the nominal size of 2 x 4 inches, even though the actual planed size is about 1.5 x 3.5 inches. A 2x6 that is 12 feet long has 12 board feet.
What does 4/4 and 8/4 mean in lumber?
It is the quarter system for hardwood thickness. The number is the thickness in quarters of an inch, measured rough before planing. 4/4 is 1 inch, 5/4 is 1 1/4 inches, 6/4 is 1 1/2 inches and 8/4 is 2 inches. After surfacing on both faces, 4/4 is usually about 13/16 inch, but it is still billed as 1 inch thick.
How many board feet are in a cubic meter?
One board foot is 144 cubic inches, which is about 0.00236 cubic meters, so one cubic meter holds about 423.8 board feet. To convert board feet to cubic meters, multiply by 0.00236. For example, 66.67 board feet is about 0.157 cubic meters. The calculator shows both values automatically.
What is the difference between board feet and linear feet?
Linear feet measure only length, while board feet measure volume by including thickness and width. Ten feet of 1 x 6 is 10 linear feet and 5 board feet, and ten feet of 2 x 12 is also 10 linear feet but 20 board feet. Hardwood is usually priced by the board foot, while trim and some softwood are priced by the linear foot.
How do I calculate the cost of lumber by the board foot?
Work out the total board feet and multiply by the price per board foot. Five 8/4 boards that are 8 inches wide and 10 feet long total 66.67 board feet, so at an example price of $10 per board foot they cost about $666.67. Enter your yard's actual price in the calculator, since prices vary by species and grade.
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