International 1/4’’ Log Rule
This rule was published in 1917 and used primarily in the eastern half of North America. It is especially popular in the New England and Quebec regions. Also, it has been adopted by the US Forest Service in several regions.
V = (0.199 x diameter in inches²) – (0.642 x diameter in inches)
V = volume in board feet for 4-foot section
D = d.i.b on small end of 4-foot length
Standardized taper of 0.125″ is used to calculate log segments. Each segment consists of 4′ cylinders and the result of the segment is rounded to the nearest 5FBM (157.3 ~ 155FBM, etc.)