# Lumber measurement

Demystifying the rules and scales for measuring lumber. July 24, 2001

Question
I am confused about BF, cf, and all the different measures. I read that a log 16" in diameter and 8' long will produce 85 BF, but plugging it into the Int formula I get 81 BF. Also the Doyle, Int and Scribner formulas produce different results. What is a 4/4 piece--is it 4" x 4" or 1" thick? What is 5/4 and 6/4?

Forum Responses
Indeed, log rules and lumber measurement are different. Also, when calculating log volumes, many rules go to the closest 10 BF.

Different rules give different results. Int 1/4-inch rule gives the closest estimate for yield for a circular mill. There is also an Int 1/8 rule that would be closer for a band mill. Scribner and Doyle underestimate the volume with smaller log sizes. The reason is that a smaller log takes more handling, so you could either measure accurately and then pay less for a smaller log due to increased handling, or just pay the same price for all volumes, but underestimate the volume for those smaller logs.

4/4 lumber (pronounced "four quarter" and meaning four 1/4-inches thickness, and four 1/4-inches totals 1 inch) is lumber that is 1.00" to 1.24" thick. This thickness is measured at the thinnest spot used to establish the grade of the piece, for hardwoods. For softwoods, 4/4 is seldom used for green lumber, but is used mainly for lumber after is planed, in which case, 4/4 means 0.75" thick at the time of planing.

5/4 would be five 1/4" or a minimum of 1.25" for hardwoods, etc. 6/4 is 1-1/2" minimum, etc.