Considering this lumber sales site, what is a board foot?

I am use to seeing lumber measured width by height, but these products are measured thickness by board feet.

  • 1
    I happen to see those Walnut boards on sale at MacBeath (the 4/4 one) when I was there the other week, and they seemed to be about 8–10" W. However, they were also 8-10' long. I would advise you to call them, they're exceedingly friendly and helpful. Jan 17, 2016 at 7:27

2 Answers 2


A board foot is a volume of wood 1 inch by 12 inches by 12 inches; i.e., 144 cubic inches.

If the board is 1/2" thick and 12" wide, one board foot would be 24" long.

If the board is 2" thick and 6" wide, one board foot would be 12" long.

Note that although rough lumber closer to advertised size than dimensional lumber, it is still often sold in nominal sizes; i.e., even the dimensions of rough lumber may be slightly larger or (more likely) slightly smaller than advertised.

  • Based on the measurements in the linked lumber, how can I deduce the length without knowing the width?
    – nipponese
    Jan 17, 2016 at 5:08
  • 3
    You cannot. Note that the website you referenced says, "...Lumber Packs contain random-width boards, about 48 inches long, surfaced and straight-lined." So you will get 1 or more boards about 48" long and adding up to however many board feet you purchase.
    – rob
    Jan 17, 2016 at 5:16

As rob pointed out a board ft. 144 cubic inches.

When dealing with rough cut lumber that is always how it is calculated for sale. Partially because it is NOT the final dimensions of the board, you will need to plane and join the sides making it smaller.

Boards you find in Menards and Home Depot already have had this finishing process done and are selling a board with the finished dimensions. But if you measure them with a tape, often it will say 1" x 12" board, but it is really 3/4" x 11.5". Same as a 2x4 is really 1.5" x 3.5".

Now when buying this lumber, you also need to realize that you can get it in 4/4, 6/4, 8/4 and sometimes 5/4. This is how many 1/4" thick the board was when they cut it. so a 4/4 board dried might be 7/8" thick. It is still counted as 4/4 or 1" for calculating board feet.

a 8/4 board will still (mostly) be the same price / board ft. as a 4/4 board, but realize that you will get 1/2 as many, since it is twice as thick and you are getting '2' boards in one.

Generally these are going to be either 8' (most common) or 10' boards and they will vary a bit in width. Rarely do they have boards under 6" wide and usually not greater than 10". If they do, they usually say. And when you buy them, they will send you a mix.

Exotics can come in any size, even 3" x 2" x 3', but then I've always seen that stated as 'remnants' to get a box of cutoffs.

  • I was about to edit your answer but then decided to post a comment instead so you could consider editing. A standard 2x4 is really 1.5" x 3.5". Even materials from 40 or 45 years ago were not 1.75" inches thick. Jan 27, 2016 at 10:23
  • @michael you are correct about the size; until about 1970 the standard size for a 2x4 was 1 5/8" x 3 5/8". Since then the standard size has been such that for a nominal dimension of 6 or less, subtract 1/2"; for dimensions greater than 6 subtract 3/4". Thus a nominal 4x12 is actually 3 1/2" x 11 1/4" and you pay for 4" x12".
    – Ast Pace
    Feb 4, 2016 at 16:42
  • doh! typing to fast and not thinking... meant to fix the 1.75" vs 1.5" when Mike pointed it out
    – bowlturner
    Feb 4, 2016 at 16:46

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