Board Foot Calculator: Lumber Volume Estimator
Calculate the volume of lumber in Board Feet (FBM).
Board Foot Calculator: Lumber Volume & Cost Estimator
A board foot (abbreviated FBM or BF) is a standard unit of volume measurement for hardwood and softwood timber in North America. One board foot represents a volume equal to a 12-inch wide by 12-inch long board that is 1 inch thick (equivalent to 144 cubic inches or 1/12 of a cubic foot).
Lumber yards and hardwood suppliers price specialty wood (such as oak, walnut, maple, and cherry) per board foot rather than by linear foot because board footage accounts for total wood volume across varying thicknesses and widths.
How to Calculate Board Feet (Step-by-Step)
- 1Measure board thickness in inches (using nominal or rough thickness, e.g., 4/4 = 1 inch, 8/4 = 2 inches).
- 2Measure board width in inches.
- 3Measure board length in feet (or in inches divided by 12).
- 4Multiply Thickness (in) × Width (in) × Length (ft).
- 5Divide the result by 12 to calculate total Board Feet (BF = (T × W × L) ÷ 12).
- 6If length is in inches: BF = (Thickness × Width × Length in inches) ÷ 144.
- 7Multiply total board feet by quantity and price per board foot to calculate total lumber cost.
Worked Example: Calculating Board Feet for Hardwood Lumber
Suppose you are buying 8 pieces of rough 8/4 White Oak that measure 6 inches wide and 10 feet long:
1. Calculate Single Board Footage: (2 inches thick × 6 inches wide × 10 feet long) ÷ 12 = 120 ÷ 12 = 10 Board Feet per board.
2. Total Project Board Footage: 10 BF × 8 boards = 80 Board Feet total.
3. Calculate Total Cost: If White Oak is priced at $8.50 per board foot: 80 BF × $8.50 = $680.00 total material cost (add 10–15% waste factor for trimming knots and warp).
Board Feet Reference Chart for Common Lumber Sizes
| Nominal Size (in) | Length (Feet) | Board Feet (1 Piece) | Board Feet (5 Pieces) | Board Feet (10 Pieces) |
|---|---|---|---|---|
| 1×4 | 8 ft | 2.67 BF | 13.33 BF | 26.67 BF |
| 1×6 | 10 ft | 5.00 BF | 25.00 BF | 50.00 BF |
| 1×8 | 12 ft | 8.00 BF | 40.00 BF | 80.00 BF |
| 2×4 | 8 ft | 5.33 BF | 26.67 BF | 53.33 BF |
| 2×6 | 10 ft | 10.00 BF | 50.00 BF | 100.00 BF |
| 2×8 | 12 ft | 16.00 BF | 80.00 BF | 160.00 BF |
| 2×10 | 12 ft | 20.00 BF | 100.00 BF | 200.00 BF |
| 4×4 | 8 ft | 10.67 BF | 53.33 BF | 106.67 BF |
| 8/4 Rough (2") × 8" | 10 ft | 13.33 BF | 66.67 BF | 133.33 BF |
Board Foot Calculator: Frequently Asked Questions
What is the difference between a linear foot and a board foot?
A linear foot measures only the length of a board regardless of width or thickness. A board foot measures total 3D cubic volume (144 cubic inches).
What do quarter designations (4/4, 5/4, 8/4) mean in hardwood lumber?
Hardwood lumber thickness is expressed in quarter-inch fractions. 4/4 (four-quarter) is 1 inch rough thickness, 5/4 is 1.25 inches, 6/4 is 1.5 inches, and 8/4 is 2 inches thick.
Do you use nominal or actual dimensions when calculating board feet?
Hardwood is measured using actual rough dimensions before surfacing. Softwood dimensional lumber (like framing 2×4s) is usually priced by piece or linear feet, but if calculated in board feet, nominal sizes (2×4) are standard in volume formulas.
How much extra waste factor should I order for woodworking projects?
Order 15% to 20% extra board footage for rough hardwood to account for defects, sapwood, checking, jointing, and planing waste.
How many board feet are in a cord of wood?
A full cord of stacked firewood (128 cubic feet of space) contains approximately 80 to 90 solid board feet of usable wood equivalent.
How do I convert cubic feet to board feet?
Multiply total cubic feet by 12 (since 1 cubic foot contains exactly 12 board feet).