How to Calculate Board Feet

By Jay Newland

To calculate board feet, multiply the thickness in inches by the width in inches by the length in feet, then divide by 12. A 2 by 6 that is 10 feet long is 10 board feet.

Pricing a Lumber Order?See the tools in our lumber section.

View Lumber Calculators

What Is a Board Foot?

A board foot is a measure of lumber volume. University of Wisconsin forestry guidance defines it as a piece of wood 12 inches wide, 12 inches long, and 1 inch thick, which is 144 cubic inches.

Board Feet by Board Size and Length

Use this chart for common sizes. The figures use nominal sizes, the sizes on the label.

Board	8 ft	10 ft	12 ft	16 ft
1 x 4	2.67	3.33	4.00	5.33
1 x 6	4.00	5.00	6.00	8.00
1 x 8	5.33	6.67	8.00	10.67
2 x 4	5.33	6.67	8.00	10.67
2 x 6	8.00	10.00	12.00	16.00
2 x 8	10.67	13.33	16.00	21.33
2 x 10	13.33	16.67	20.00	26.67
2 x 12	16.00	20.00	24.00	32.00
4 x 4	10.67	13.33	16.00	21.33

The Formula

Thickness and width are in inches, and length is in feet.

Board feet = thickness x width x length / 12

If you measure the length in inches too, divide by 144 instead.

Board feet = thickness x width x length / 144

Worked Example

Here is the math for 12 boards, each a 2 by 4 that is 8 feet long.

2 in x 4 in x 8 ft = 64
64 / 12 = 5 1/3 board feet per board, or 5.33 rounded
5 1/3 x 12 boards = 64 board feet

Nominal Size and Actual Size

Lumber is smaller than its label. A 2019 review of the American Softwood Lumber Standard proposed wording that describes nominal size as a label that does not reflect the dressed size, and gives a dry 2 by 4 as 1 1/2 by 3 1/2 inches.

The Wisconsin fact sheet makes the same point. A 10 foot 2 by 6 comes to 10 board feet by its nominal size, but about 6.875 board feet by its actual size of 1 1/2 by 5 1/2 inches. Check which one your supplier uses before you compare prices.

Board Feet per Linear Foot

If you buy many lengths of one size, work out the board feet in one foot of board, then multiply by the total length. Multiply thickness by width and divide by 12.

Board	Board Feet per Linear Foot
1 x 4	0.33
1 x 6	0.50
1 x 8	0.67
2 x 4	0.67
2 x 6	1.00
2 x 8	1.33
2 x 10	1.67
2 x 12	2.00
4 x 4	1.33

For example, 100 linear feet of 2 by 6 is 100 board feet, and 100 linear feet of 2 by 4 is 67 board feet.

Hardwood Thickness in Quarters

Hardwood is often described in quarters of an inch. Woodworkers Source explains that 4/4, called four quarter, means about 1 inch of rough thickness. The same site says 8/4 means about 2 inches thick.

Use the rough thickness in the formula if that is how your supplier measures, and ask if you are not sure. A board that has been planed is thinner than its rough size.

Measuring a Stack

The same formula gives an estimate for a stack of equal length boards, if you use its height and width in inches. The Wisconsin fact sheet gives a stack 36 inches high and 60 inches wide, with boards 8 feet long, as 1,440 board feet. That assumes a tight stack, so gaps and spacers between boards mean less lumber than the estimate shows.

36 in x 60 in x 8 ft = 17,280
17,280 / 12 = 1,440 board feet

Comparing Prices

Some lumber is priced per board, and some per board foot. To compare them, divide the price of a board by its board feet.

An 8 foot 2 by 4 is 5.33 board feet
$8 per board / 5.33 board feet = $1.50 per board foot

The $8 is a sample figure. Use the price on your own quote.

From Board Feet to Cost

Multiply the board feet by the price per board foot. At a sample price of $4 per board foot, 64 board feet costs $256. Prices vary by species, grade, and supplier, so use your own quote.

Frequently Asked Questions

These cover the questions that come up most often.

How Many Board Feet Are in a 2x4x8?

By nominal size, a 2 by 4 that is 8 feet long is 5.33 board feet.

What Is the Difference Between a Board Foot and a Linear Foot?

A linear foot only measures length. A board foot also counts thickness and width, so a wider board has more board feet at the same length.

Is a Board Foot the Same as a Square Foot?

Only for a board 1 inch thick. A 2 inch thick board has 2 board feet for each square foot of face.

How Many Board Feet Are in a Cubic Foot?

A cubic foot is 1,728 cubic inches, so it holds 12 board feet of 144 cubic inches each.

Sources

Every figure in this guide comes from the sources below, or from the math shown.