Lumber
What Is a Board Foot in Lumber?
A clear explanation of the board foot, how to calculate board feet for hardwood and lumber, nominal vs actual sizes, and how to estimate project cost.
Walk into a hardwood dealer and you will see prices like "$9.50/BF". BF stands for board foot, a unit of volume used to price lumber. Understanding it makes it much easier to compare prices and plan woodworking projects.
The definition
One board foot is the volume of a board 1 inch thick, 12 inches wide and 12 inches long — 144 cubic inches. A board 2 in thick, 6 in wide and 12 in long is also one board foot, because it has the same volume.
12 board feet make one cubic foot. One board foot is about 0.00236 cubic metres.
How to calculate board feet
Example
Formulas
- Board feet = Thickness (in) × Width (in) × Length (ft) ÷ 12
- or, all in inches: Thickness × Width × Length ÷ 144
Example
Example: a walnut board
- 8/4 (2 in) thick, 7 in wide, 9 ft long
- 2 × 7 × 9 ÷ 12 = 10.5 BF
- At $14/BF: 10.5 × 14 = $147
Understanding quarter thickness
Rough hardwood thickness is expressed in quarters of an inch:
| Quarter | Rough thickness | Typical surfaced thickness |
|---|---|---|
| 4/4 | 1 in | ≈ 13/16 in |
| 5/4 | 1¼ in | ≈ 1 1/16 in |
| 6/4 | 1½ in | ≈ 1 5/16 in |
| 8/4 | 2 in | ≈ 1¾ in |
Board feet are normally calculated on the rough (nominal) thickness, even if the board has been surfaced. Surfaced thicknesses vary by mill, so treat the right-hand column as approximate.
Nominal vs actual dimensions
Softwood construction lumber is named by nominal size: a 2×4 is about 1½ × 3½ in. When suppliers quote board feet for dimensional lumber they usually use the nominal size, so a 2×4×8 is 5.33 BF. If in doubt, ask how they measure.
Planning a project in board feet
- Make a cut list of every part with its finished dimensions.
- Calculate board feet for each part using the rough thickness you will buy.
- Add 20–30% for defects, saw kerf and grain matching. Highly figured or knotty stock may need more.
- Multiply by the price per board foot.
Try the Board Foot Calculator
Board feet, cubic volume and cost for hardwood and lumber purchases.
Frequently asked questions
How many board feet are in a 1×6×8?
Using nominal dimensions: 1 × 6 × 8 ÷ 12 = 4 board feet.
Is a board foot the same as a linear foot?
No. A linear foot measures length only. A board foot measures volume, so it depends on thickness and width too.
How do I calculate board feet for live-edge slabs?
Measure the average width (several measurements across the slab), multiply by thickness and length, then divide by 12 or 144 as appropriate.
About the author
Written by the BuildCalcWorld Editorial Team. Our guides explain standard estimating methods with worked examples you can verify. Material properties vary by product and region, so always confirm specifications with your supplier. Published . Learn more about us.