For example, if a motor has 400 ft-lbs. of torque and stalls a particular converter at 3,000rpm. We can predict the new stall speed if torque is increased to say 500 ft-lbs. This Calculator isn't perfect. It won't work if the engines have wildly different torque curve, for example. Also this would be based on full throttle RPM. (max torque being applied) And it won't tell if a particular converter will hold together under markedly increased torque. But it gives a decent ballpark estimate and serves to illustrate a basic aspect of torque converter function. For most street and street/strip, you probably want a stall in the 2,500-3,500rpm range. But do not buy an off the shelf converter thinking it will give you the advertised stall unless it has been shown to do so on an identical setup. Speak to the manufacturer first to be sure you are getting what you need for your particular combo.