Torque Wrench Adapter Extended Equations & Calculator

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Torque Wrench Adapter Extended Equations & Calculator

The following is the calculations one would use to determine the actual torque applied when using an extension or crow-foot. The torques wrench adapter extended calculator requires a java enabled browser.

When using a torque wrench adapter which decreases the distance from the torque wrench drive to location of applied force (handgrip location) use the following formulas to obtain the correct torque wrench reading or setting.

OPEN: Torque Wrench Adapter Extended Equations & Calculator

OPEN: Torque Wrench Adapter Extended Equations & Calculator


T = Target or actual Torque required (lb-in),
Y = Torque setting or reading to obtain desired torque "T" (in-lbs),
L = Distance between applied force and Torque wrench drive center (in),
E = Distance between torque wrench drive center and crows foot drive center (in),
F = Applied force (Lbs).

Note: Length units can be mm, ft or other as long as the units used are consistent when calculating:

Torque Proof

Due to the difference in length from the applied force F to the fastener adapter the Torque reading or setting on torque wrench is changed to Y to obtain a desired torque of T.


Y = F · L (Torque wrench setting or reading)

The actual torque applied at the drive center of the extension:

T = F · ( L + E )

Rearrange for F:

F = Y / L
F = T / ( L + E )

F = F therefore substituting we get:

Y / L = T / ( L + E )
Y = T · L / ( L + E )


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