Torque wrench calibration is very important and depending on the accuracy required can be very expensive. NovaTork brand torque wrench is each calibrated at three points: 20%, 60%, and 100% of their range. The accuracy usually is +/-4% accuracy in clockwise direction from 20% to 100% Max. Torque, which is typical of high-quality torque wrenches and is more than sufficient for normal uses. Accuracy of +/-4% means that if your fastener should be tightened to a specification of 100 lb.ft, the torque wrench will click to indicate a proper torque somewhere between 96 and 104 lb.ft.