Hong Life CalculatorsUnderstanding the board feet calculator — concept and principle
This calculator converts lumber dimensions into board feet, the traditional North American unit for selling timber, and into cubic metres, then multiplies by the price per board foot. Woodworkers and builders use it to compare prices, order hardwood by volume and budget a project.
How it is calculated
- Board feet = thickness (in) × width (in) × length (ft) ÷ 12 × number of pieces.
- Cubic metres = board feet × 0.0023597.
- Cost = board feet × price per board foot.
The principle
One board foot is the volume of a board 1 inch thick, 12 inches wide and 12 inches long: 144 cubic inches, or 1/12 of a cubic foot. Multiplying thickness and width in inches by length in feet gives a volume in "inch-inch-feet"; dividing by 12 turns that into board feet because 12 in × 1 in × 1 ft = 1 board foot. Since 1 inch is exactly 2.54 cm, 144 in³ equals about 0.00236 m³, so 1 m³ is about 424 board feet.
Worked example
- Inputs: 2 in × 6 in boards, 8 ft long, 10 pieces, 4 per board foot (USD).
- One piece: 2 × 6 × 8 ÷ 12 = 8 board feet.
- Ten pieces: 8 × 10 = 80 board feet.
- Volume: 80 × 0.0023597 ≈ 0.189 m³.
- Cost: 80 × 4 = $320.00.
| Thickness (in) | Board feet |
|---|---|
| 0.5 | 20 |
| 1 | 40 |
| 1.5 | 60 |
| 2 | 80 |
| 2.5 | 100 |
| 3 | 120 |
| 4 | 160 |
How to read the result
Price per board foot lets you compare boards of different sizes fairly. Be aware of nominal and actual sizes: in North American softwood, a "2 × 6" is planed to about 1.5 × 5.5 in, yet it is commonly measured on its nominal size, so the 80 board feet above contain only about 55 board feet of actual wood. Hardwood is often sold by rough thickness in quarters of an inch (4/4, 8/4), before planing. Add 10–20% for defects and cutting waste when ordering.
Common mistakes
- Entering length in inches instead of feet; the formula expects feet.
- Mixing nominal and actual dimensions when comparing suppliers.
- Forgetting that planing and cutting reduce usable volume.
Frequently asked questions
How many board feet are in a cubic metre?
About 424, since 1 ÷ 0.0023597 ≈ 423.8.
What is a linear foot?
Simply length in feet regardless of cross-section; mouldings and trim are often priced that way.
How do I calculate board feet with all dimensions in inches?
Multiply thickness × width × length in inches and divide by 144.
Sources: NIST, Voluntary Product Standard PS 20, American Softwood Lumber Standard · USDA Forest Products Laboratory, Wood Handbook (FPL-GTR-190)