How to Convert Board Feet to Linear Feet

You priced a project in board feet, walked into the yard, and the boards are sold by the foot of length. Now you need to turn one into the other. It is a common snag, and the fix is a short formula once you see why the two numbers are not the same thing.

Here is the short version. A board foot is a measure of volume: one foot by one foot by one inch thick. A linear foot is just length, one foot of board no matter how wide or thick it is. So you can only convert between them once you know the board's width and thickness.

The formula

To go from board feet to linear feet, use this:

linear feet = (board feet x 144) / (nominal thickness x nominal width)

The 144 is the number of cubic inches in a board foot (12 x 12 x 1). Thickness and width are the nominal size, the name on the board, not the planed actual size. That keeps the math consistent with how the board feet were figured in the first place.

To go the other way, from linear feet back to board feet:

board feet = (linear feet x nominal thickness x nominal width) / 144

A worked example

Say a plan calls for 20 board feet of 1x6, and the yard sells 1x6 by the linear foot. Plug it in:

linear feet = (20 x 144) / (1 x 6)

Run it step by step: 20 x 144 = 2,880. Divide by (1 x 6 = 6) and you get 480 inches, which is 40 linear feet. So 20 board feet of 1x6 is 40 linear feet of board. That makes sense: a 1x6 holds half a board foot per running foot, so it takes twice as many running feet to reach the same volume.

Now try a thicker board. 20 board feet of 2x6:

linear feet = (20 x 144) / (2 x 6) = 2,880 / 12 = 240 inches = 20 linear feet.

Same board feet, but because the 2x6 is twice as thick, you need half the length. The thicker or wider the board, the fewer linear feet it takes to reach the same board-foot total.

Quick conversion chart

Linear feet needed to reach 10 board feet, by nominal size:

Nominal size	Board feet per linear foot	Linear feet for 10 bf
1x4	0.33	30
1x6	0.50	20
1x8	0.67	15
1x12	1.00	10
2x4	0.67	15
2x6	1.00	10
2x8	1.33	7.5
2x12	2.00	5

The pattern: a 1x12 and a 2x6 both hold exactly one board foot per linear foot, so their linear-feet total equals their board-foot total. Anything narrower or thinner needs more length, anything wider or thicker needs less.

What about board feet to square feet?

Square feet is a different question because it ignores thickness. To cover a surface, you care about width and length, not how thick the board is. To get the square feet a board covers, multiply its actual width by its length in feet. A 1x6 that is 8 feet long covers about (5.5 inches / 12) x 8 = 3.67 square feet of face, even though it is 4 board feet. Use square feet for coverage like flooring or paneling, and board feet for buying and pricing volume.

Why nominal, not actual

It is tempting to measure the real 3.5-inch face of a 2x4 and use that. Do not, for pricing math. The trade figures board feet at nominal size, so both sides of your conversion have to use nominal size or the numbers drift apart. If you switch to actual size on one side only, your linear-foot count will come out wrong and your material order with it. When in doubt, keep everything nominal and let the board foot calculator handle the arithmetic.

Common questions

How many linear feet are in a board foot? It depends on the board. For a 1x12 or a 2x6, one board foot is one linear foot. For a 1x6, one board foot is two linear feet. Divide 144 by (thickness x width) to get the linear feet in a single board foot of that size.

Is a linear foot the same as a board foot? No. A linear foot is length only. A board foot is volume, one square foot at one inch thick. They match only for a board that holds exactly one board foot per running foot, like a 1x12.

How do I convert board feet to linear feet quickly? Multiply board feet by 144, then divide by nominal thickness times nominal width. Or use the per-size figures in the chart above.

Which should I use to buy lumber? Use whatever the yard prices in. Softwood at a home center is often sold by the linear foot, while hardwood and rough stock are sold by the board foot. Convert so your cut list and your order speak the same units. The board foot vs linear foot guide covers when each shows up.

The takeaway

Board feet is volume, linear feet is length, and the bridge between them is the board's nominal thickness and width. Multiply board feet by 144, divide by thickness times width, and you have the running feet to buy. Keep everything nominal, and when the sizes get messy, run it through the board foot calculator instead of doing it by hand.