# Board foot calculator for lumber and timber

> Board foot calculator: board feet, linear feet, volume and cost for a stack of lumber, at nominal size and at the dressed size of a 2x4, 2x6 and more.

Interactive version: https://www.calcopenly.com/construction/board-foot-calculator
Subject: Construction and home calculators

A board foot is 144 cubic inches of wood, a piece 1 in thick, 12 in wide and 1 ft long. Board feet for a stack are thickness (in) × width (in) × length (ft) ÷ 12 × pieces. Linear feet are length × pieces, and cost follows the basis the yard prices by: per piece, per board foot or per linear foot.

The default, ten 2 × 6 boards 8 ft long, is 80 board feet and 80 linear feet, costing 75.00 at 7.50 each. Softwood board feet are counted on the nominal size, but a dry 2 × 6 is dressed to 1½ × 5½ in, so the wood delivered is 55 board feet.

Turn off nominal sizing for rough-sawn hardwood or metric timber, which is measured as it is. Metric pieces convert at 1 board foot = 2.359737216 litres.

## Inputs

- **Thickness**
- **Width**
- **Length**
- **Pieces**
- **Sizes are nominal (a 2 × 6 is really 1½ × 5½ in)**: Lumber yards price softwood by nominal size; turn off for rough-sawn or metric timber measured as is.
- **Price is** (options: Per piece, Per board foot, Per linear foot)
- **Price**

## Results

- Board feet (BF) — main result
- Board feet at dressed size (BF)
- Dressed size
- Linear feet (ft)
- Linear metres (m)
- Volume at the sizes entered (m³)
- Cost

## Formula

$$
\text{BF} = \frac{t_{\text{in}} \times w_{\text{in}} \times L_{\text{ft}}}{12} \times \text{pieces}
$$

## Worked examples

### Ten 2 × 6 × 8 ft at 7.50 each

- Thickness: 2 in
- Width: 6 in
- Length: 8 ft
- Pieces: 10
- Price is: Per piece
- Price: 7.5
- **Board feet: 80 BF**
- **Board feet at dressed size: 55 BF**
- **Linear feet: 80 ft**
- **Cost: 75.00**
- **Dressed size: 1.5 × 5.5 in**
- Checked against: Hand calculation: 2 × 6 × 8 / 12 = 8 BF × 10 = 80; dressed 1.5 × 5.5 × 8 / 12 × 10 = 55 (PS 20 sizes)

### Edge: 1 × 12 in × 1 ft is one board foot

- Thickness: 1 in
- Width: 12 in
- Length: 1 ft
- Pieces: 1
- Price is: Per board foot
- Price: 4.5
- **Board feet: 1 BF**
- **Board feet at dressed size: 0.7 BF**
- **Cost: 4.50**
- Checked against: Definition: 1 BF = 144 in³ = 1 in × 12 in × 12 in; dressed 0.75 × 11.25 × 12 / 144 = 0.703125

### Metric 50 × 150 mm × 3 m timber, 20 pieces, per linear foot

- Thickness: 50 mm
- Width: 150 mm
- Length: 3 m
- Pieces: 20
- Sizes are nominal (a 2 × 6 is really 1½ × 5½ in): no
- Price is: Per linear foot
- Price: 2
- **Board feet: 190.7 BF**
- **Volume at the sizes entered: 0.45 m³**
- **Linear feet: 196.85 ft**
- **Cost: 393.70**
- Checked against: Python decimal: 0.05 × 0.15 × 3 × 20 = 0.45 m³ ÷ 0.002359737216 m³ per BF = 190.70; 60 m ÷ 0.3048 = 196.85 ft × 2

## Questions

### 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 8 ft long is 2 × 6 × 8 ÷ 12 = 8 board feet, so ten of them are 80. With all three sides in inches, divide by 144 instead: a board 1 × 12 × 12 in is exactly 1 board foot.

### Do you use nominal or actual size for board feet?

Nominal size for surfaced softwood: a 2 × 4 is counted as 2 × 4 in although it measures about 1½ × 3½ in. Hardwood is measured at its actual size, and rough hardwood thickness is given in quarters, 4/4 for 1 in and 8/4 for 2 in. With nominal sizing on, this calculator shows both: ten 2 × 6 × 8 ft are 80 BF nominal and 55 BF dressed.

### What are the actual dimensions of a 2x4?

1½ × 3½ in (38 × 89 mm) once dried and planed. Other 2× sizes lose ½ in of width up to 6 in and ¾ in above that: a 2 × 6 is 1½ × 5½, a 2 × 8 is 1½ × 7¼, a 2 × 10 is 1½ × 9¼ and a 2 × 12 is 1½ × 11¼ in. A nominal 1 in board is ¾ in thick, and a 4 × 4 is 3½ × 3½ in.

### How many board feet are in a cubic metre?

423.78. One board foot is 144 in³, exactly 2.359737216 litres, and 1 m³ ÷ 0.002359737216 m³ = 423.776. The metric example uses this: 20 pieces of 50 × 150 mm timber 3 m long are 0.45 m³, which is 190.70 board feet.

### What does MBF mean in lumber pricing?

MBF means 1,000 board feet; MFBM and MBFT mean the same, and MMBF is a million board feet. A thousand board feet is 83.33 ft³, or 2.36 m³. A price of 600 per MBF is 0.60 per board foot, so an 8-board-foot 2 × 6 × 8 ft costs 4.80 at that rate.

### How accurate is the board foot calculator?

Accuracy depends on your inputs and the method's assumptions. Decimal arithmetic uses 50 significant digits, but estimates, numerical methods and source data can be less precise; the displayed rounding does not remove those limits. It is checked against 3 worked examples whose answers come from independent sources; for example, “Ten 2 × 6 × 8 ft at 7.50 each” is checked against Hand calculation: 2 × 6 × 8 / 12 = 8 BF × 10 = 80; dressed 1.5 × 5.5 × 8 / 12 × 10 = 55 (PS 20 sizes).

### Where does the method come from?

USDA Forest Products Laboratory — Wood Handbook (FPL-GTR-282), lumber sizes and measurement; Board foot — 144 in³, exactly 2.359737216 L; NIST Voluntary Product Standard PS 20 — American Softwood Lumber Standard (dressed sizes).

## Sources

- [USDA Forest Products Laboratory — Wood Handbook (FPL-GTR-282), lumber sizes and measurement](https://research.fs.usda.gov/treesearch/62200)
- [Board foot — 144 in³, exactly 2.359737216 L](https://en.wikipedia.org/wiki/Board_foot)
- NIST Voluntary Product Standard PS 20 — American Softwood Lumber Standard (dressed sizes)