An apparatus and method of sorting power transmission belts into groups of substantially equal length. The apparatus is entirely automatic and includes mechanism for transferring seriatim the respective belts from a supply to a measuring drive mechanism. The belt being measured is driven under tension and the length and rideout concurrently determined and fed to a computer. In the event the belt is found to be outsized but capable of being brought into the desired range by grinding the sides thereof, grinding mechanism of the apparatus is actuated to adjust the configuration suitably. The apparatus includes mechanism for discarding outsized belts which cannot be so adjusted. The apparatus includes mechanism for transferring the belts from the measuring drive system to a conveyor and associated mechanism for sorting the measured belts as a function of a signal provided by the computer.