How to calculate the torque required for tightening & loosening the lid from a jar?

As a general rule, the amount of torque is about half of the diameter of the cap. Torque is expressed in inches per pound.

If you care to know exactly how much torque you need to open the jar, for example, you can measure the jar lid and then find a way to gauge the force needed to break the lid free. The equation for torque T is: T = F x r where F = force (oz or lb) and r = radius (in. or ft).

Applying too much pressure to a closure can actually increase the chances of product leakage.

Over-torquing may cause some points on the cap to have more pressure then others, which could result in an improper seal. If the cap is applied with too little torque, the container may leak or the closure could come off too easily.