a formula log rule derived from the mathematical equation used to calculate the volume of a cylinder —note 1. the rule assumes 1/16-in (0.16 cm) shrinkage for each inch (2.54 cm) of board thickness and a taper of 0.5-in (1.27 cm) for each 4-ft (1.2 m) log section —note 2. in one form it assumes a 1/8-in (0.32) kerf; in a modified form, assuming a 0.25-in (0.64 cm) kerf, it is one of the official rules of the USDA Forest Service —see Doyle rule, international quarter-inch rule, Scribner rule This definition last updated 07/17/2008