A board foot is a piece 12 in long, 12 in wide and 1 in thick: 144 cubic inches. Hardwood dealers price by it.
Board foot calculator
Use nominal sizes for softwood (a 2x4 is 2 by 4) and the rough thickness for hardwood (4/4, 8/4).
Enter your numbers to see the result.
The formula
Board feet = thickness (in) x width (in) x length (ft) / 12.
- A 2 x 4 x 8 ft board: 2 x 4 x 8 / 12 = 5.33 board feet.
- A 1 x 6 x 10 ft board: 5 board feet.
- Ten 8/4 x 8 in x 8 ft hardwood boards: 106.7 board feet.
Nominal and actual sizes
Softwood lumber is named by its rough size and then dried and planed. Under the American Softwood Lumber Standard (PS 20), a dry 2x4 is 1-1/2 x 3-1/2 in, a 2x6 is 1-1/2 x 5-1/2 in and a 2x8 is 1-1/2 x 7-1/4 in. Board feet are figured on the nominal size. See the full lumber size chart.
Hardwood is sold rough by quarter-inch thickness: 4/4 is 1 in, 8/4 is 2 in.
Sources
Sources last checked 1 November 2026.
Frequently asked questions
How many board feet is a 2x4x8?
5.33 board feet.
Do you use actual or nominal size for board feet?
Nominal size for softwood dimension lumber, and the rough thickness for hardwood (4/4, 5/4, 8/4).
What is 8/4 lumber?
Rough hardwood 2 in thick (eight quarters of an inch).