Understanding Board Feet: The Standard Lumber Measurement
A board foot is the standard unit of volume used throughout the lumber industry in North America. Whether you're buying hardwood from a sawmill, estimating material costs for a furniture project, or calculating yields from rough lumber, understanding board feet is essential for every woodworker.
What Is a Board Foot?
One board foot (abbreviated BF or bd ft) equals a volume of wood that is one inch thick, twelve inches wide, and twelve inches long—totaling 144 cubic inches. This standardized measurement allows buyers and sellers to compare lumber of different dimensions on an equal basis.
Unlike linear feet (which only measures length) or square feet (which measures area), board feet accounts for all three dimensions of a piece of lumber. This makes it the most accurate way to measure and price solid wood.
The Board Foot Formula
The formula for calculating board feet is straightforward:
Board Feet = (Thickness in inches × Width in inches × Length in feet) ÷ 12
Alternatively, if all measurements are in inches:
Board Feet = (Thickness × Width × Length) ÷ 144
Common Examples
- 1" × 12" × 12" = 1 board foot (the definition)
- 2" × 6" × 8' = (2 × 6 × 8) ÷ 12 = 8 board feet
- 4/4 × 8" × 10' = (1 × 8 × 10) ÷ 12 = 6.67 board feet
- 8/4 × 6" × 6' = (2 × 6 × 6) ÷ 12 = 6 board feet
Nominal vs. Actual Dimensions
When working with rough-sawn lumber from a sawmill, the stated thickness is typically the actual thickness. However, when purchasing surfaced lumber (S2S or S4S), be aware that the actual dimensions are smaller than the nominal size. A "1-inch" surfaced board is actually about 13/16" thick after planing.
For accurate material estimation, always measure your lumber or ask the supplier whether prices are based on nominal or actual dimensions. Most hardwood dealers price based on the rough-sawn (nominal) thickness before surfacing.
Lumber Thickness Notation
Hardwood lumber thickness is traditionally expressed in "quarters" of an inch:
- 4/4 = 1 inch (four quarters)
- 5/4 = 1.25 inches
- 6/4 = 1.5 inches
- 8/4 = 2 inches
- 12/4 = 3 inches
- 16/4 = 4 inches
This notation originated in the days when sawmills cut lumber in quarter-inch increments. Understanding this system helps when communicating with lumber suppliers.
Pricing by the Board Foot
Lumber prices vary dramatically based on species, grade, and availability. As of recent years, common domestic hardwoods like red oak or poplar might range from $3-8 per board foot, while premium species like walnut or cherry can run $8-15 per board foot or more. Exotic species and figured woods command even higher prices.
When estimating project costs, remember to factor in waste. A typical furniture project might require 20-30% more lumber than the finished piece contains, accounting for defects, grain matching, and cutting waste.
Tips for Accurate Estimation
- Measure carefully: Use the actual dimensions of your lumber, not nominal sizes
- Account for waste: Add 20-30% to your calculated needs for cutting waste and defects
- Consider grain direction: Long pieces may require longer stock that yields more waste
- Check for defects: Knots, checks, and sapwood reduce usable yield
- Factor in surfacing: If you're surfacing rough lumber, you'll lose 1/8" to 1/4" per face
Our board foot calculator handles all the math for you, accepting measurements in inches, millimeters, or feet. Simply enter your lumber dimensions and get instant results you can use for pricing, ordering, or project planning.