What Is a Board Foot? Lumber Measurement Explained
Hardwood lumber is not sold by the linear foot the way construction lumber is at a home center. It is sold by the board foot, a volume measure that lets a supplier price a stack of boards of different widths and thicknesses with one number. Understanding the unit is what makes it possible to compare prices, estimate a project and check an invoice. The arithmetic is simple once you know which dimensions it uses.
Quick answer: One board foot is 144 cubic inches of lumber, which is a piece 1 inch thick, 12 inches wide and 12 inches long. The formula is thickness in inches times width in inches times length in feet, divided by 12. A 1 inch thick, 6 inch wide, 8 foot long board is 4 board feet, and hardwood commonly sells for roughly $3 to $12 per board foot by species and grade.
The board foot formula
Multiply thickness in inches by width in inches by length in feet, then divide by 12. The divisor exists because a board foot is 144 cubic inches, and the formula already accounts for length being measured in feet rather than inches: 12 inches of length times 1 inch of thickness times 12 inches of width is exactly 144 cubic inches. Thickness and width stay in inches while length is in feet, which is the step people most often mix up. Multiply by the number of identical pieces at the end.
Why hardwood is priced this way
Softwood dimension lumber is milled to a few standard sizes and sold by length, so a linear foot price is simple and fair. Hardwood arrives in random widths and in thicknesses measured by quarters of an inch. Pricing by volume handles that variation with a single number, so a supplier can quote per board foot regardless of whether the boards are four inches wide or ten. It also makes it possible to compare a thick narrow board fairly against a thin wide one.
Nominal versus actual dimensions
A 2x4 is a nominal size; its actual dimensions are near 1.5 inches by 3.5 inches.
A 1 inch thick hardwood board is usually surfaced to about 13/16 inch.
Hardwood is priced from rough thickness, not from the surfaced measurement.
A 1x6 construction board measures roughly 3/4 inch by 5.5 inches in practice.
Board feet for hardwood are calculated from nominal thickness, not actual thickness.
Working through a cut list
A cut list gives the finished sizes you need. For each line, convert to the thickness and width the lumber is sold at, apply the formula, then add waste for defects, planing and mistakes. Hardwood often arrives with knots, checks and wane that you have to cut around, so a waste factor of 15% to 30% is common on small projects. Total the board feet, add the waste factor, and round up, because hardwood is usually bought in whole boards rather than an exact figure.
Board feet versus linear feet and square feet
Linear feet measure length only, and they work when every piece is the same width and thickness, which is why trim and framing use them. Square feet measure area and suit sheet goods, flooring and siding. Board feet measure volume, and they are the right unit when width varies and thickness matters, which is the normal case for hardwood. If a supplier quotes a hardwood price per linear foot, ask what thickness and width that price assumes before comparing it with anything else.
Frequently Asked Questions
How do you calculate board feet?
Multiply thickness in inches by width in inches by length in feet, then divide by 12. A 2 inch thick, 6 inch wide, 10 foot long board is 2 times 6 times 10 divided by 12, which is 10 board feet. Multiply by the quantity at the end when you are pricing several identical pieces.
How many board feet are in a 2x4?
An 8 foot 2x4 is calculated from its nominal dimensions: 2 times 4 times 8 divided by 12, which is about 5.33 board feet. In practice, construction lumber is sold by the piece or by linear feet rather than by board feet, so the figure mainly matters when you compare volume, weight or shipping cost.
Is a board foot the same as a linear foot?
No. A linear foot measures length alone. A board foot measures volume, specifically 144 cubic inches. Two boards can be identical in linear feet yet differ widely in board feet if their widths or thicknesses are different, which is exactly why hardwood suppliers price by volume.
How much waste should I add for hardwood?
Fifteen percent is a reasonable minimum for a simple project in clear stock, and 25% to 30% is common when boards contain defects you must cut around or when grain matching matters. Thin resawing, wide glued-up panels and highly figured species usually justify the higher end of that range.
What does a board foot of hardwood cost?
It varies widely with species, grade and region, from inexpensive domestic species at the low end to imported and highly figured woods far above that. Boards sold as shorts or with visible defects cost less than long clear stock. Ask your supplier for the current price in your area rather than relying on a national average.