How to use this board foot calculator
- Enter the thickness and width in inches (use nominal thickness for rough lumber, e.g. 4/4 = 1 in).
- Enter the length.
- Enter how many boards and, optionally, the price per board foot.
Example
Six 2 × 8 inch boards, 10 ft long, contain 80 BF. At $4.50 per board foot they cost about $360.
What to know before you buy
Nominal versus actual size
Construction lumber is named by its rough size before drying and planing: a 2×4 actually measures 1.5 × 3.5 inches. Hardwood is sold rough by quarters (4/4, 8/4) and priced by the board foot of its nominal size.
Planning a project
List every part of your project, calculate the board feet for each and add 20–30% for defects, knots and cutting waste. Buying boards slightly longer than needed gives you room to cut around flaws.
Board feet per 8 ft board
| Nominal size | Board feet |
|---|---|
| 1 × 4 | 2.67 BF |
| 1 × 6 | 4 BF |
| 1 × 8 | 5.33 BF |
| 2 × 4 | 5.33 BF |
| 2 × 6 | 8 BF |
| 2 × 10 | 13.33 BF |
| 4 × 4 | 10.67 BF |
Formula
Board feet = thickness (in) × width (in) × length (in) ÷ 144. 12 board feet = 1 cubic foot.
Tips from the pros
- Add 15–25% extra when buying rough hardwood to allow for defects and planing.
- Thickness in quarters: 4/4 is 1 inch, 5/4 is 1.25 inches, 8/4 is 2 inches (rough).
- Softwood construction lumber is usually sold per piece, hardwood per board foot.
Common mistakes to avoid
- Using actual planed sizes (e.g. 1.5 × 3.5 in for a 2×4) when the price is based on nominal size.
- Mixing feet and inches: board feet use inches for thickness and width but feet for length.
Frequently asked questions
What is a board foot?
A volume of wood equal to 144 cubic inches, e.g. 1 in × 12 in × 12 in.
Do I use nominal or actual size?
Hardwood dealers usually price rough lumber by nominal thickness (4/4, 5/4, 8/4) measured before planing.
How many board feet in a 2x4x8?
5.33 board feet (2 × 4 × 96 ÷ 144).
How do I convert board feet to cubic feet?
Divide board feet by 12.