How to Calculate Lumber in Board Feet
Board feet is the standard unit for measuring and pricing lumber volume. Unlike square feet, board feet account for thickness—a 1-inch-thick board takes up twice the volume of a ½-inch board of the same dimensions.
The Formula
Board Feet = (Thickness in inches × Width in inches × Length in feet) / 12
Or equivalently:
Board Feet = (Thickness × Width × Length in inches) / 144
Step-by-Step Examples
Example 1: One 1×6×8 board (nominal 1 inch × 6 inch × 8 feet) Board feet = (1 × 6 × 8) / 12 = 48 / 12 = 4 board feet
Example 2: One 2×10×12 board Board feet = (2 × 10 × 12) / 12 = 240 / 12 = 20 board feet
Nominal vs. Actual Lumber Dimensions
A "2×4" is not actually 2 inches × 4 inches. Nominal sizes refer to rough-cut dimensions before drying and planing.
| Nominal | Actual Size |
|---|---|
| 1×4 | 0.75 × 3.5 in |
| 1×6 | 0.75 × 5.5 in |
| 2×4 | 1.5 × 3.5 in |
| 2×6 | 1.5 × 5.5 in |
| 4×4 | 3.5 × 3.5 in |
Board feet pricing uses nominal dimensions even though actual dimensions are smaller—this is standard industry practice.
Calculating a Project's Total Board Feet
For a deck using twenty 2×6×16 boards: Board feet per piece = (2 × 6 × 16) / 12 = 16 bf Total = 20 × 16 = 320 board feet
Add 10–15% for waste: 320 × 1.12 = 359 bf → order 360 board feet
Use our board feet calculator for any lumber dimensions or quantity.