BF = (T × W × L) ÷ 12
T = Thickness in inches
W = Width in inches
L = Length in feet
BF = Board Feet
Important Note
Results are estimates based on nominal lumber dimensions. Actual lumber sizes may vary due to milling, finishing, and drying. Always verify with your lumber supplier.
A board foot (BF) is the standard unit of measurement for lumber volume in the United States and Canada. One board foot is equivalent to a piece of wood that is 1 inch thick, 12 inches wide, and 12 inches long, or 144 cubic inches of wood. This measurement system has been used by the lumber industry for over a century and remains the primary way hardwood lumber is bought and sold.
Understanding board feet is essential for woodworkers, carpenters, and contractors because lumber pricing is typically quoted per board foot. Whether you're building furniture, framing a house, or working on any woodworking project, knowing how to calculate board feet helps you accurately estimate material costs and order the right amount of lumber.
When working with lumber, it's important to understand the difference between nominal and actual dimensions. Nominal dimensions are the names used to describe lumber sizes (like 2×4 or 1×6), while actual dimensions are the true measurements after milling and drying. For example, a nominal 2×4 actually measures 1.5" × 3.5".
| Nominal Size | Actual Size |
|---|---|
| 1×4 | 3/4" × 3-1/2" |
| 1×6 | 3/4" × 5-1/2" |
| 2×4 | 1-1/2" × 3-1/2" |
| 2×6 | 1-1/2" × 5-1/2" |
| 2×10 | 1-1/2" × 9-1/4" |
| 4×4 | 3-1/2" × 3-1/2" |
For board foot calculations at lumberyards, nominal dimensions are typically used. However, for hardwood lumber sold rough (unfinished), actual measurements are used. Always confirm with your supplier which measurement convention they use.
The board foot measurement is used extensively in various woodworking and construction scenarios:
Furniture Making
Calculate material needs for tables, chairs, cabinets, and other furniture projects. Helps estimate costs when using premium hardwoods.
Deck Building
Determine lumber quantities for deck boards, joists, and railings. Essential for accurate project budgeting.
Home Framing
Estimate framing lumber for walls, floors, and roofs. Helps contractors price jobs accurately.
Custom Millwork
Calculate wood needed for trim, molding, and architectural details. Important for custom home builds.
Add for Waste
Always add 10-20% extra to your board foot calculations to account for defects, cutting waste, and mistakes. For complex projects with many cuts, consider adding even more.
Verify Measurements
Double-check all measurements before placing orders. Remember that lumber is often sold in even lengths (6', 8', 10', 12'), so factor this into your planning.
Consider Wood Species
Different wood species have different prices per board foot. Hardwoods like oak, walnut, and maple are significantly more expensive than softwoods like pine or spruce.