What Kirk is trying to say is a log is not necessarily a tree. A tree can have more than on log.

The amount of lumber from a log can be estimated using a "log scale" table. Factors used to estimate the amount of lumber are diameter on the small end of the log and length.

Also different sawmills can cut different lengths. All sawmills have a maximum length they can cut. So a 24' log for one mill might be two 12' logs to another. Lots of variables.

The most common scale books (calculators) used are Doyle, Scribner and International. All give very close to the same volume figure. In a given geographical are only one book is used. I have no idea what is used south of the USA border.

Here's a link: http://www.woodweb.com/cgi-bin/calculators/calc.pl?calculator=log_volume I think there is a metric calculator on the same web site.

Today's large sawmills are all computerized with band saw mills and yields from conifers trees for constructions wood can reach 200% of scale. Part of that is the fact that construction lumber in the USA is cut smaller than actual stated sizes ( a 2" x 6" is actually 1 1/2" x 5 1/2") and sawing accuracy is much better today than when the scale books were written, thus oversize raw boards to be planed to standard sizes are not needed only sanded.

A band mill has a 20% guaranteed increase of yield over scale because of the thinner kerf of the saw blade on medium to large logs but at a price. Band mills are more complicated than wheel sawmills. Kerf (blade thickness) for a band mill runs from 1/16 to 1/8" where a wheel saw blade can exceed 5/16" or even 3/8".

Does that help?