How to Calculate Board Feet
Board feet (BF) is the standard unit of measurement for lumber volume in North America. One board foot equals a piece of wood 12 inches long, 12 inches wide, and 1 inch thick. The formula is straightforward:
Board Feet = (Thickness × Width × Length) ÷ 12
Where thickness and width are in inches and length is in feet. This measurement is critical when purchasing hardwood lumber, which is almost always sold by the board foot.
Nominal vs Actual Dimensions
When buying dimensional lumber at a home center, a "2×4" actually measures 1.5" × 3.5". However, board foot calculations for pricing typically use nominal dimensions. When buying rough-sawn hardwood from a mill, the lumber is measured at full nominal thickness before planing.
Tips for Buying Lumber
- Always buy 10-15% extra to account for waste, defects, and cutting errors
- Check for warping, cupping, and knots before purchasing
- Store lumber flat and off the ground to prevent moisture damage
- Compare prices between home centers and local sawmills for hardwoods