Board foot calculator

Board feet for a single board or a whole order. One line per size: quantity, thickness, width and length. The total updates as you type.

Total board feet

49.88 BF

With 20% waste allowance: 59.85 BF. That is 4.156 cubic feet (0.1177 m³) in 74 linear feet of boards.

Item	Qty	Size (T × W × L)	BF each	BF total
rails	4	1" × 6" × 8'	4.00	16.00
legs	2	2" × 6" × 6'	6.00	12.00
top	3	1 1/4" × 7" × 10'	7.29	21.88

The formula

A board foot is 144 cubic inches. With thickness and width in inches and length in feet:

board feet = thickness × width × length(ft) / 12
or, with every dimension in inches, thickness × width × length / 144
cubic feet = board feet / 12, and one board foot is 0.00236 m³

That is the whole calculation. There is no rounding in the result: if you need a yard's style tally, round each line the way that yard does.

Worked example

The default list is a small table in hardwood: four 4/4 × 6" × 8' boards for rails, two 8/4 × 6" × 6' boards for legs, and three 5/4 × 7" × 10' boards for the top.

Rails: 1 × 6 × 8 / 12 = 4 BF each, 16 BF for four
Legs: 2 × 6 × 6 / 12 = 6 BF each, 12 BF for two
Top: 1.25 × 7 × 10 / 12 = 7.29 BF each, 21.88 BF for three

Together that is 49.88 board feet. With a 20% allowance for milling and defects, order about 60 board feet. At, say, $12 per board foot, the difference between 50 and 60 is $120, which is why the allowance is worth deciding on before you go rather than at the rack.

Board feet in common softwood sizes

Tallied at nominal size, which is how board-foot prices for dimension lumber are quoted.

Nominal	BF per foot	8 ft	10 ft	12 ft	16 ft
1×4	0.333	2.67	3.33	4.00	5.33
1×6	0.500	4.00	5.00	6.00	8.00
1×8	0.667	5.33	6.67	8.00	10.67
1×10	0.833	6.67	8.33	10.00	13.33
1×12	1.000	8.00	10.00	12.00	16.00
2×4	0.667	5.33	6.67	8.00	10.67
2×6	1.000	8.00	10.00	12.00	16.00
2×8	1.333	10.67	13.33	16.00	21.33
2×10	1.667	13.33	16.67	20.00	26.67
2×12	2.000	16.00	20.00	24.00	32.00
4×4	1.333	10.67	13.33	16.00	21.33
6×6	3.000	24.00	30.00	36.00	48.00

Hardwood thickness in quarters

Rough hardwood is sold by thickness in quarter inches. The surfaced thickness below is the commonly quoted standard for boards surfaced on two sides (S2S); what you actually get depends on how flat the rough board was and how much the mill takes off.

Quarters	Rough (tally) thickness	Typical S2S thickness
4/4	1"	13/16"
5/4	1 1/4"	1 1/16"
6/4	1 1/2"	1 5/16"
8/4	2"	1 3/4"
12/4	3"	2 3/4"

Board feet are always counted on the rough thickness. You pay for 1" of 4/4 walnut even though the finished part is 3/4".

Where it stops being reliable

The arithmetic is exact, so the only way to get a wrong answer is to use the wrong dimensions. Be consistent about nominal versus actual sizes, and remember that random-width hardwood is measured board by board: a "6-inch" board might be 5 3/4" or 6 1/2". For a real order, measure the boards you pick and enter each one. For money rather than volume, the lumber cost calculator converts between board-foot, linear-foot and per-piece prices.

Common questions

What is a board foot?

A unit of volume: 144 cubic inches, which is a board 1 inch thick, 12 inches wide and 12 inches long. Any board with the same volume is also one board foot, such as 2 inches thick, 6 inches wide and 12 inches long. Hardwood lumberyards price almost everything by the board foot.

Do I use the nominal or the actual size?

The size the lumber is sold by. Rough hardwood is tallied at its nominal thickness in quarters (4/4 counts as 1 inch) and its measured width and length. Softwood dimension lumber is tallied at nominal size, so a 2x4 counts as 2 by 4 even though it measures 1 1/2 by 3 1/2. If you are working out how much wood is really in a surfaced board, use the actual size instead, and expect a smaller number.

How much extra should I buy?

There is no single right figure. Rough lumber loses thickness and width to jointing and planing, and length to checked ends and defects. Many woodworkers add something between 15 and 30 percent to the calculated total, and more for highly figured wood, for projects that need grain or colour matching, or when the lumber is low grade. The waste box applies whatever percentage you choose.

How do I enter thickness in quarters?

Type it as a fraction: 4/4, 5/4, 8/4. The calculator reads 8/4 as 2 inches. Plain inches such as 0.75 or 3/4 also work.

Why does the lumberyard tally come out different from mine?

Yards measure random-width boards individually, often round each board to the nearest whole board foot, and some measure width at the narrow end or deduct for wane. Some also round lengths down to the whole foot. Your total is the exact volume; theirs follows their tally rules, which are worth asking about.