But a nominal 6 inch width is 5 1/2 inches, so if you rip that 12 inch board in half, allowing for 1/8th inch kerf, your home-ripped boards are going to each be 1/16th wider than boards you would buy at the store.

So when you get common softwood lumber a board foot of 1 x 12 would actually measure 1 foot long by 11.25 wide by .75 thick. If you were to by nominal 1x2's, the loss would be greater. these only measure 1 1/2 inches wide. Six of these, side by side would only measure 9 inches, but that's what you woudl get in a board foot of 1x2s--a piece .75 thick, 12 inches long, and equivalent to 9 inches wide.

Should you decide you need 1x2s and figure on ripping your own from a 1x12, with 5 rip cuts taking out 5/8ths inch of material, you'll be splitting the remaining 10 5/8-wide board into 6 pieces which are a bit over 1 3/4 inches wide. But why do that when with 6 rip cuts, removing 3/4 inch of stock in those 1/8th inch kerfs, you can actually rip the remaining 10.5 of good wood into seven, not six 1x2s.

Yes this is confusing--and the lumberyards are usually the winners. There are some exceptions. I've run into some places where the employees weren't sure how the management set the prices, or the management had their own rules on figuring boardfeet. They would look at the listed price per board foot, and if the wood measured 3/4 inch thick they would charge you 75 percent of the listed rate. Sometimes they would figure the actual width of a board, as well.

The moral here is to ask how rates are calculated at that particular lumberyard before buying, or comparing their price with the competition.

Caveat Emptor (let the buyer beware)

In April 2003 The United States Department of Agriculture (USDA) published a study on this (http://www.treesearch.fs.fed.us/pubs/22353) and found that after observing data from 14 different mills, starting in 1996:
"The width of the dry, 4/4 thickness, red oak lumber sample was significantly influenced by lumber grade, lumber length, and mill. The dominant lumber widthclass was 5.00 to 6.75 inches (47 % of all boards). Boards in the FAS and FAS-1F grades were wider than those in the No. 1, No. 2A, and No. 3A Common grades, and these were wider than the Selects grade boards. There was significant variability in lumber size attributes between mills, supporting the contention that each mill must collect its own data on lumber size and quality characteristics for optimal decision making"

The entire report is available here: http://www.fs.fed.us/ne/newtown_square/publications/other_publishers/OCR/ne_2003_wiedenbeck002.pdf

Hope this helps

PGJ