# How many board feet is my lumber?

Computes board feet (length × width × thickness ÷ 144 cubic inches) per board and for several boards, and the cost at a price per board foot.

- Page: https://www.acalculator.org/construction/board-foot-calculator
- JSON spec: https://www.acalculator.org/construction/board-foot-calculator.json
- Version: 7ba8929743c8

## Default answer

Example with the default inputs (Length 8 ft, Width 6 in, Thickness 1 in, Number of boards 1): Boards of 8 ft × 6 in × 1 in, 1 in all, make 4 board feet.

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| l | Length | The length of one board. |
| w | Width | The width of one board. |
| t | Thickness | The thickness of one board. |
| quantity | Number of boards | How many boards of this size. |
| price | Price per board foot | What one board foot costs, to work out the total cost. Leave empty to skip the cost. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| total | Total board feet | Board feet for all the boards: board feet per board × number of boards. |
| each | Board feet per board | Length × width × thickness of one board, divided by 144 cubic inches. |
| volume | Volume | The total wood volume: 1 board foot is 1/12 of a cubic foot. |
| cost | Total cost | Total board feet × price per board foot. |

## Method

board feet = length × width × thickness ÷ 144 in³ (length in feet × width in inches × thickness in inches ÷ 12)

## Assumptions

- One board foot is 144 cubic inches: a board 12 inches long, 12 inches wide and 1 inch thick.
- Use the size you pay for. Softwood lumber is often sold by its nominal size (a 2×4 is billed as 2 in × 4 in), while its actual size is smaller (1.5 in × 3.5 in).
- The cost is total board feet × price per board foot, with no waste allowance.

## Worked examples

1. l = 2.4384, w = 0.1524, t = 0.0254, quantity = 1 gives total = 4, each = 4. Source: Wikipedia, Board foot (a board foot is 144 cubic inches: 12 in × 12 in × 1 in). https://en.wikipedia.org/wiki/Board_foot.
2. l = 2.4384, w = 0.254, t = 0.03175, quantity = 1 gives total = 8.333333. Source: Wikipedia, Board foot (a board foot is 144 cubic inches: 12 in × 12 in × 1 in). https://en.wikipedia.org/wiki/Board_foot.
3. l = 3.048, w = 0.0889, t = 0.0381, quantity = 12, price = $2.50 gives each = 4.375, total = 52.5, cost = $131.25. Source: Wikipedia, Board foot (a board foot is 144 cubic inches: 12 in × 12 in × 1 in). https://en.wikipedia.org/wiki/Board_foot.

## FAQ

### What is a board foot?

A board foot is a unit of volume used for lumber, equal to 144 cubic inches (12 inches long by 12 inches wide by 1 inch thick). Unlike square footage, which measures area, board footage measures volume. By definition, one board foot of lumber is one square foot that is one inch thick. You use it when purchasing multiple boards of lumber in various sizes.

### How do you calculate board feet?

The board foot formula is: Board Feet = Length (ft) × Width (in) × Thickness (in) ÷ 12. Pay special attention to the units! The length should be in feet, while the width and thickness should be in inches. For example, for a board that's 8 feet long, 10 inches wide, and 1.25 inches thick: Board feet = 8 × 10 × 1.25 ÷ 12 = 8.33 BF.

### How do you measure a board foot?

Take a rectangular piece of lumber, measure the length in feet, width in inches, and thickness in inches. Then multiply all three numbers together and divide by 12. The formula is: Board Feet = (Length in feet) × (Width in inches) × (Thickness in inches) ÷ 12.

### How many board feet are in a 2x4?

It depends on which size you count. By its nominal size (2 in × 4 in), which lumber yards often use for pricing, a 2x4 has 2 × 4 × length ÷ 12 board feet: 6 ft = 4 BF, 8 ft = 5.33 BF, 10 ft = 6.67 BF, 12 ft = 8 BF, 16 ft = 10.67 BF. Its actual size is 1.5 in × 3.5 in, which gives 1.5 × 3.5 × length ÷ 12: 6 ft = 2.63 BF, 8 ft = 3.5 BF, 10 ft = 4.38 BF, 12 ft = 5.25 BF, 16 ft = 7 BF.

### What is the difference between a board foot and a linear foot?

A board foot is a measure of volume (accounts for width, length, and thickness), while a linear foot is a measure of length only. Board feet are used for lumber pricing and are the standard unit for hardwood. Linear feet are common for trim and molding and don't account for width or thickness.

### How do you calculate the board feet in a log?

To calculate board feet in a log, you can use either the Doyle rule or the International ¼-inch rule table. Measure the diameter of the shorter end of the log (not including bark) in inches and the length in feet, then look up where the two values meet on the table. The Doyle rule as a formula: ((Diameter - 4)/4)² × Length. This calculator is for sawn boards, not logs.

### How much does a board foot of oak weigh?

A board foot is 1/12 of a cubic foot, so its weight is the wood density ÷ 12. Oak varies from about 37 to 56 lb/ft³ (600 to 900 kg/m³) depending on the variety and moisture, so a board foot of oak weighs about 3.08 to 4.67 lb (1.4 to 2.1 kg).

### How many board feet are there in 320 square feet?

There are no board feet in 320 square feet, as board feet is a measure of volume and square feet is a measure of area. However, for an area that is 320 square feet with a depth of 1 inch, there are 320 board feet present. Board feet measure volume while square feet measure area.

### What is a board foot insulation?

Board foot insulation is a measurement of how much volume spray foam insulation can cover. A board foot is a volume of 1 ft × 1 ft × 1 in, so you estimate the volume you need to fill before buying your spray foam insulation by finding the square footage of the space. A board foot is also a common unit of measure for lumber in the USA and Canada.

## Sources

- Wikipedia, Board foot (a board foot is 144 cubic inches: 12 in × 12 in × 1 in). https://en.wikipedia.org/wiki/Board_foot