What is a board foot, and how to calculate board feet

A board foot is a piece of lumber 12" long, 12" wide and 1" thick, or the same 144 cubic inches in any shape. To calculate board feet, multiply thickness × width in inches by the length in feet and divide by 12: a 2x4 that is 10 feet long is 2 × 4 × 10 ÷ 12 = 6.67 board feet.

Free to print, no sign-up. US Letter, 1 page, 30 KB. Every number is worked out by Construction Calculator 1.1.1's own formulas.

Board feet by nominal size and length

Nominal size	Per foot	8 ft	10 ft	12 ft	14 ft	16 ft
1x4	0.33	2.67	3.33	4	4.67	5.33
1x6	0.5	4	5	6	7	8
1x8	0.67	5.33	6.67	8	9.33	10.67
1x10	0.83	6.67	8.33	10	11.67	13.33
1x12	1	8	10	12	14	16
2x4	0.67	5.33	6.67	8	9.33	10.67
2x6	1	8	10	12	14	16
2x8	1.33	10.67	13.33	16	18.67	21.33
2x10	1.67	13.33	16.67	20	23.33	26.67
2x12	2	16	20	24	28	32
4x4	1.33	10.67	13.33	16	18.67	21.33
4x6	2	16	20	24	28	32
6x6	3	24	30	36	42	48

Board feet = thickness × width (inches) × length (inches) ÷ 144, on the nominal size (a 2x4 is counted as 2" × 4"), to 2 decimal places.

Board feet per linear foot by thickness and width

Thickness	4" wide	6" wide	8" wide	10" wide	12" wide
1/2"	0.33	0.5	0.67	0.83	1
3/4"	0.33	0.5	0.67	0.83	1
4/4 (1")	0.33	0.5	0.67	0.83	1
5/4 (1-1/4")	0.42	0.63	0.83	1.04	1.25
6/4 (1-1/2")	0.5	0.75	1	1.25	1.5
8/4 (2")	0.67	1	1.33	1.67	2

Hardwood thickness is often given in quarters of an inch (4/4 = 1"). Construction Calculator counts stock thinner than 1" as 1" thick, which is why the 1/2" and 3/4" rows match 4/4.

The board foot formula

With every measurement in inches: thickness × width × length ÷ 144. With the length in feet, as lumber is sold: thickness × width × length ÷ 12. Both give the same answer, because a foot of length is 12" and 144 ÷ 12 = 12.

How many board feet are in a 2x4x10?

6.67 board feet: 2 × 4 × 10 ÷ 12. A 2x4x8 is 5.33 board feet, a 2x6x8 is 8, and a 4x4x8 is 10.67. The first table gives the common sizes from 1x4 to 6x6 at lengths from 8' to 16', and the board feet in one foot of each.

Nominal size, not the size of the wood

Board feet are counted on the lumber’s nominal size: a 2x4 counts as 2" × 4", though a dry 2x4 is dressed to 1-1/2" × 3-1/2" (PS 20-20, Table 3). The Forest Products Laboratory’s Wood Handbook defines the count on the nominal thickness and width and the actual length. So a 2x4x8 is 5.33 board feet on the bill, while the wood in it is 1-1/2" × 3-1/2" × 96", or 3.5 board feet of actual volume.

Boards thinner than 1 inch

The Wood Handbook says lumber with a nominal thickness under 1" is calculated as 1", and Construction Calculator does the same, which is why the 1/2" and 3/4" rows in the second table match 4/4. The softwood lumber standard, PS 20-20, multiplies by “the nominal thickness in inches or fraction of an inch”, so a yard may tally thin stock either way: ask your supplier which they use.

Hardwood thickness in quarters

Hardwood is often sold by quarters of an inch: 4/4 is 1", 5/4 is 1-1/4", 6/4 is 1-1/2" and 8/4 is 2". A 5/4 board 6" wide holds 0.63 board feet per foot of length (1.25 × 6 ÷ 12 = 0.625).

Board feet, square feet and linear feet

A board foot measures volume, a square foot measures the face of a board, and a linear foot is length only. For 1"-thick stock one square foot of face is one board foot; for 2" stock it is two. A 2x6 happens to hold exactly 1 board foot per linear foot (2 × 6 ÷ 12), so a 2x6 that is 14' long is 14 board feet.

Pricing lumber by the board foot

Multiply the board feet by the price per board foot. Ten 2x4x8s are 53.33 board feet; at $1.25 a board foot that is $66.67. These are the figures the app’s board feet tool shows when you first open it.

The board feet formula

Construction Calculator 1.1.1 counts board feet as the larger of the thickness and 1", times the width, times the length in inches, divided by 144, rounded to 2 decimal places; the tables here are worked out the same way.