The standard atmosphere (atm) is a pressure unit defined as exactly 101,325 pascals, representing the average atmospheric pressure at sea level on Earth. It serves as a reference point in chemistry for gas law calculations and in engineering for rating pressure vessel capacities. One atmosphere equals approximately 1.01325 bar, 14.696 psi, or 760 mmHg.

PSI (pounds per square inch) is an imperial pressure unit equal to about 6,894.76 pascals, the standard measurement for tire pressure, compressed air systems, and hydraulic equipment in the United States. Almost every American gas station air pump and pressure washer displays ratings in PSI, making it one of the most recognized pressure units worldwide. One PSI equals approximately 0.06895 bar or 6.895 kPa.