Board foot
| board foot | |
|---|---|
| Unit of | Volume |
| Symbol | FBM |
| Conversions | |
| 1 FBM in ... | ... is equal to ... |
| SI base units | ≈0.002359737 m3 |
| US Customary | 1⁄12 ft3 |
The board foot or board-foot is a unit of measurement for the volume of lumber in the United States and Canada.[1] It equals the volume of a board that is one foot (30.5 cm) in length, one foot in width, and one inch (2.54 cm) in thickness, or exactly 2.359737216 liters. Board foot can be abbreviated as FBM (for "foot, board measure"), BDFT, or BF. A thousand board feet can be abbreviated as MFBM, MBFT, or MBF. Similarly, a million board feet can be abbreviated as MMFBM, MMBFT, or MMBF.
Until the 1970s, in Australia and New Zealand, the terms super foot and superficial foot were used with the same meaning.[2][3][4]
Description
[edit]One board foot equals:
- 1 ft × 1 ft × 1 in
- 12 in × 12 in × 1 in
- 12 ft × 1 in × 1 in
- 144 cu in
- 1⁄12 cu ft
- ≈ 2,360 cubic centimeters
- ≈ 2.360 liters
- ≈ 0.002360 cubic meters or steres
- 1⁄1980 Petrograd Standard of board
Usage
[edit]
The board foot is used to measure both rough (unprocessed) lumber and planed (surfaced) lumber. Rough lumber is measured before drying and planing, using its full sawn dimensions. Planed lumber, such as standard softwood "two by four" boards sold at retail, is measured using nominal dimensions—typically 2 by 4 inches (50 mm × 100 mm)—even though the actual size is only about 1+1⁄2 in × 3+1⁄2 in (38 mm × 89 mm) after processing. Despite the reduction in size due to drying and planing, nominal dimensions are still used when calculating board feet for surfaced softwood lumber. This convention simplifies pricing and standardization but may result in board footage values that do not reflect the true volume of wood in the final product. Essentially, the nominal dimensions assume a larger volume than the actual board contains, which is especially relevant when estimating material needs or costs. [5] For planed lumber, board footage is calculated using the nominal width and thickness, and the actual length of the board. This reflects the lumber’s original rough size before drying and surfacing. For rough lumber, board footage is calculated using the actual width, thickness, and length of the board.
See dimensional lumber for a full explanation of nominal versus actual dimensions. Briefly, for softwoods:
- Subtract 1⁄4 inch (6 mm) from nominal sizes under 2 inches,
- Subtract 1⁄2 inch (13 mm) from nominal sizes between 2 and 8 inches,
- Subtract 3⁄4 inch (19 mm) for nominal sizes over 8 inches.[6]
The system is less complex for hardwoods, because actual board measurements are used.
Board Foot Conversions
[edit]A board foot (BDFT) represents a measure of lumber volume. Other units commonly used in the lumber industry include pieces (pcs), thousand board feet (MBF), and linear or lineal feet (LFT).[7] Conversions between these units require basic dimensional information.
Pieces to Board Foot Conversion
[edit]To convert from pieces to board feet, use the dimensions of the lumber: T = thickness (in inches) W = width (in inches) L = length (either in inches or feet)
Two common formulas are used, depending on whether length is measured in inches or feet:
- Using inches:
BDFT = (T × W × Lin) / 144
Example:
2 × 4 × 96 / 144 = 5.33 board feet
- Using feet:
BDFT = (T × W × Lft) / 12
Example:
2 × 4 × 8 / 12 = 5.33 board feet
These formulas assume the dimensions are nominal and the lumber is softwood. For hardwoods or surfaced lumber, actual dimensions may be used instead. See Dimensional lumber for more detail.
See also
[edit]References
[edit]- ^ Board foot
- ^ Rowlett, Russ. "How Many? A Dictionary of Units of Measurement". Retrieved 2007-01-30.
- ^ Burger, Les. "Cutting Timber on Springbrook in 1935". Archived from the original on September 17, 2007. Retrieved 2007-11-06. Archived 2007-09-17 at the Wayback Machine
- ^ Holgate, Alan. "The Bendigo Monier Arch Bridges". Archived from the original on 2007-07-02. Retrieved 2007-11-06. Archived 2007-07-02 at the Wayback Machine
- ^ Sluga, Doug (March 21, 2025). "Board Footage Calculator for Lumber Measurements". Today’s Homeowner. Retrieved April 25, 2025.
- ^ "Softwood Lumber - Dimensions". The Engineering ToolBox. Retrieved April 25, 2025.
- ^ "Lumber Calculators". Wisconsin Lumber. Retrieved April 25, 2025.