The complete guide to board feet calculation, with real examples and an easy-to-use calculator.
A board foot (often abbreviated "bf" or "BF") is the standard unit of measurement for lumber volume. It's defined as a piece of wood that measures exactly 1 inch thick × 12 inches wide × 12 inches long.
Understanding board feet is essential if you're:
Calculating board feet is straightforward. Use this formula:
Important: Use the actual dimensions of the lumber, not the nominal (named) size. A 2×4 is actually 1.5" × 3.5", not 2" × 4".
Let's calculate the board feet for a 2×4 that's 8 feet long:
Here's a quick reference table for common lumber sizes at various lengths:
| Nominal Size | Actual Size | 8 ft | 10 ft | 12 ft | 16 ft |
|---|---|---|---|---|---|
| 1×4 | 0.75" × 3.5" | 2.3 bf | 2.9 bf | 3.5 bf | 4.7 bf |
| 1×6 | 0.75" × 5.5" | 3.7 bf | 4.6 bf | 5.5 bf | 7.3 bf |
| 1×8 | 0.75" × 7.25" | 4.9 bf | 6.1 bf | 7.3 bf | 9.7 bf |
| 2×4 | 1.5" × 3.5" | 4.7 bf | 5.9 bf | 7.0 bf | 9.3 bf |
| 2×6 | 1.5" × 5.5" | 7.3 bf | 9.2 bf | 11.0 bf | 14.7 bf |
| 2×8 | 1.5" × 7.25" | 9.9 bf | 12.3 bf | 14.7 bf | 19.6 bf |
| 2×10 | 1.5" × 9.25" | 12.3 bf | 15.4 bf | 18.5 bf | 24.7 bf |
| 2×12 | 1.5" × 11.25" | 15.0 bf | 18.8 bf | 22.5 bf | 30.0 bf |
| 4×4 | 3.5" × 3.5" | 9.3 bf | 11.7 bf | 14.0 bf | 18.7 bf |
Let's say you're building a 12×16 ft deck with 2×6 joists spaced 16 inches apart, and you plan to use 2×6 boards for decking.
Joists: You'll need about 10 joists (one every 16", plus perimeter). At 16 feet each:
Decking: Calculating coverage for the 192 sq ft deck surface using 2×6 boards with 1/8" gaps:
Total: ~427 board feet for your deck project.
At $0.60 per board foot (typical pricing), that's about $256 in lumber. Use our calculator to verify exact coverage for your specific dimensions.
Many beginners make the mistake of calculating board feet using the nominal (named) dimensions:
The difference is significant! Using nominal dimensions overstates the volume by about 30%. Always use actual dimensions for accurate pricing.
Don't do the math by hand. Use our free board feet calculator — it handles multiple pieces and gives you the total instantly.
Go to Calculator →Already have a full list of cut lengths for a project? The Cut List Optimizer goes a step further — it figures out the fewest stock boards to buy and exactly what to cut from each one.
Check out our full lumber reference chart for actual dimensions of every common size, or use our interactive calculator to compute board feet instantly.