Bolt Preload from Torque

WHAT THIS SCREEN ANSWERS

Tightening torque is commonly used as a proxy for bolt preload, but it is an imprecise proxy because most input torque is lost to friction. Lubrication, coating, thread condition, washer condition, bearing surface, tool accuracy, and installation practice can change the relationship. This page therefore shows a preload range instead of presenting one confident tension.

Enter applied tightening torque, nominal diameter, and a justified low and high nut factor. MechPlane calculates the corresponding range using the torque-tension proxy. A wider nut-factor range creates a wider preload range, making the uncertainty explicit. It does not infer a nut factor from a bolt grade or from a generic torque chart.

Actual preload matters because it affects clamp load, separation resistance, fatigue behavior, embedment, joint slip, and gasket or component damage. The torque method may be adequate for ordinary work, but it is not a substitute for a validated tightening process where preload is critical. Angle control, direct tension measurement, or procedure validation may be needed.

Use this screen to frame a preliminary joint question, then confirm the fastener, thread, washer, lubrication, torque tool, joint stack, target preload, installation sequence, and applicable standards. Do not use it as the sole basis for a safety-critical, pressure-containing, lifting, or regulated joint.