1 Psi = 51.7149326 Torr
Psi is defined as 1 pound of force applied per square inch. 1 pound per square inch (psi) equals to 6 894.75729 pascals.
Torr is 1/760 of an atm (atmospheric pressure). mmHg (millimeter of mercury) is a pressure of fluid from one millimeter of mercury. Torr and mmHg are different pressure units but the difference is very low (about 0.000015%) and they are treated as the same pressure unit in most applications. It is used in physics and engineering and mmHg is commonly used in measuring the blood pressure.