Board Foot Converter (board feet, 재/才, m³)

Understanding the board foot converter — concept and principle

Timber is priced by volume, but the volume unit depends on where you buy it. North American lumber yards use the board foot, Korean and Japanese timber markets traditionally use the jae (재, 才), and international trade and forestry statistics use cubic metres. This converter moves a lumber volume between board feet, jae, cubic metres, cubic feet and litres, which is handy when comparing quotes or converting an imported price list.

How it is calculated

The value is converted to cubic metres, then divided by the size of the target unit:

• 1 board foot = 12 in × 12 in × 1 in = 144 in³ = 2.359737216 L (exact)
• 1 cubic foot = 12 board feet
• 1 m³ ≈ 423.776 board feet
• 1 jae = 1 chi × 1 chi × 12 ja; with 1 ja = 10/33 m and 1 chi = 1/33 m, that is 120/35,937 m³ ≈ 3.3392 L
• 1 m³ ≈ 299.47 jae; 1 jae ≈ 1.4151 board feet

For a board, board feet = thickness (in) × width (in) × length (ft) ÷ 12.

The principle

Both units are slabs of a standard cross-section and length. A board foot is a one-inch-thick board one foot square, so a board's board feet simply count how many such slabs fit in it. The jae is a square stick one chi on each side and twelve ja long, the traditional measuring stick of East Asian carpentry. Because the inch is exactly 2.54 cm and the ja is defined here as exactly 10/33 m, every factor is a fixed ratio with no measurement involved.

Worked example

Default input: 100 board feet to cubic metres.

1. 100 × 144 in³ = 14,400 in³.
2. 14,400 × 16.387064 cm³ = 235,973.7 cm³ = 235.9737216 L.
3. In cubic metres: 0.2359737216 m³.
4. In jae: 0.2359737 ÷ 0.0033392 ≈ 70.668 jae; in cubic feet: 100 ÷ 12 = 8.333.

How to read the result

A cubic metre is a lot of timber: roughly 424 board feet or about 300 jae. When you compare prices, convert both to the same unit first; a price per board foot × 423.776 gives a price per m³, and the same works in any currency. Remember that sellers often quote volume from nominal sizes: a North American "2 × 4" is actually about 1.5 × 3.5 in after drying and planing, but it is still sold as 2 × 4 board feet.

Common mistakes

• Mixing nominal and actual dimensions in the same comparison.
• Forgetting that board-foot length is in feet while thickness and width are in inches.
• Assuming 1 jae is a round number of litres; it is about 3.339 L.
• Comparing green (wet) and kiln-dried lumber volumes as if they were the same; wood shrinks as it dries.

Frequently asked questions

How many board feet are in a cubic metre?

About 423.776 board feet.

How many jae are in a cubic metre?

About 299.47 jae.

How do I calculate the board feet of a plank?

Multiply thickness (in) × width (in) × length (ft) and divide by 12. A 2 × 6 board 8 ft long is 8 board feet.

Is a board foot the same as a square foot?

No. A board foot is a volume (one square foot, one inch thick); a square foot is an area.

Sources: NIST Special Publication 811 (2008), Appendix B (board foot = 2.359737 × 10⁻³ m³) · NIST Handbook 44, Appendix C, General Tables of Units of Measurement