a formula to estimate the volume (usually in board feet) of lumber that may be sawed from logs of different sizes under various assumed conditions given their length and scaling (small end) diameter —note log rules are commonly divided into four groups on the basis of derivation: (a) diagram rules, (b) formula rules, (c) rules based on actual output, and (d) hybrid rules —see Doyle rule, international log rule, international quarter-inch rule, log scale, Scribner ruleThis definition last updated 07/17/2008