The formula both ways
Linear feet = board feet × 12 ÷ (nominal thickness × nominal width)
Board feet = linear feet × nominal thickness × nominal width ÷ 12
Use the nominal size, the name on the tag, not the actual dressed size. Board feet are always counted from the nominal number, which is how lumber is priced.
Say a quote lists 240 board feet of 2x8 and you want to know how many 8 ft sticks that is. A 2x8 is 2 × 8 ÷ 12 = 1.333 board feet per foot, so 240 board feet is 240 ÷ 1.333 = 180 linear feet, which is about 22 eight-foot boards once you add for waste.
Board feet per linear foot, and linear feet in 100 board feet
| Size | Board feet per linear foot | Linear feet in 100 board feet |
|---|---|---|
| 1x4 | 0.333 | 300.0 |
| 1x6 | 0.5 | 200.0 |
| 2x4 | 0.667 | 150.0 |
| 2x6 | 1 | 100.0 |
| 2x8 | 1.333 | 75.0 |
| 2x10 | 1.667 | 60.0 |
| 2x12 | 2 | 50.0 |
| 4x4 | 1.333 | 75.0 |
| 6x6 | 3 | 33.3 |
The middle column is the handy one. A 2x6 is exactly 1 board foot per foot, so for a 2x6 the two numbers are the same. A 1x4 is only a third of a board foot per foot, so 100 board feet of 1x4 is 300 linear feet.
Why you need the size
A board foot is 144 cubic inches, a foot of a 1 inch board that is 12 inches wide. A thin, narrow board carries few board feet in each foot of length, so it takes a lot of linear feet to reach a given board foot total. A thick, wide board is the opposite. That is the whole reason a single conversion number does not exist.
For area instead of length, see the board feet to square feet calculator, or let the board foot calculator do the board feet from the size.
Frequently asked questions
How do you convert board feet to linear feet?
Multiply the board feet by 12, then divide by the nominal thickness times the nominal width. For a 2x8, that is board feet divided by 1.333.
How many linear feet are in 100 board feet of 2x4?
150.0 linear feet, because a 2x4 is 0.667 board feet per foot.
Is a linear foot the same as a board foot?
No. A linear foot is a length. A board foot is a volume, 144 cubic inches. They only match for a 1x12 or a 2x6.
Do I use the nominal or actual size?
Nominal, the name on the tag. That is how board feet are counted and how lumber is priced.