Torque Wrench Extension Calculator (Corrected Setting)

Torque Wrench Extension Calculator (Corrected Setting)

When a torque wrench needs an extension at the drive end to reach a bolt, the wrench reading no longer equals the torque delivered to the fastener: the effective lever gets longer, so the bolt receives MORE torque than the setting. Skipping this correction can over-yield a high-strength bolt by 25% or more.

The correction is simple: Setting = Target x L / (L + E), where L is the wrench's calibrated lever length (handle center to drive square) and E is the extension length parallel to the lever. Example: target 40 N.m, L = 400 mm, E = 100 mm -> set the wrench to 40 x 400/500 = 32 N.m.

Three cautions: the formula holds only for extensions parallel to the lever axis; angle head adapters change the force line and need actual calibration; pneumatic tools follow the same rule with lower accuracy - verify critical joints with the bolt-mark method. Determine your target with the torque calculator first. Zhuhai Jiali Hardware supplies precision screws with torque test data - contact us.