How to convert between PSI and MPa pressure units?

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The conversion between psi and MPa: psi is a unit of pressure, defined as pounds per square inch; 145 psi equals 1 MPa. The full English name for PSI is Pound per Square Inch. P stands for pound, S stands for square, and I stands for inch. By converting all units to metric units, it is possible to calculate that 1 bar ≈ 14.5 psi, and 1 psi = 6.895 kPa = 0.06895 bar. Regions such as Europe and the United States commonly use psi as their unit of measurement. In China, we generally use “kilograms” to describe the pressure of gases (rather than “jin”); the unit of measurement is “kg/cm^2”, where one kilogram of pressure represents one kilogram of force applied to one square centimeter. The unit commonly used abroad is “Psi”, specifically “lb/in2”, which means “pounds per square inch”. This unit is similar to the Fahrenheit scale (F). In addition, there are also pressure units such as Pa (Pascal, one newton per square meter), KPa, Mpa, Bar, millimeters of water column, and millimeters of mercury. 1 bar = 0.1 MPa = 100 KPa = 1.0197 kg/cm². 1 standard atmosphere (ATM) = 0.101325 MPa = 1.0333 bar. Since the differences between these units are small, it can be remembered as follows: 1 bar = 1 standard atmosphere (ATM) = 1 kg/cm² = 100 KPa = 0.1 MPa. The conversion for psi is as follows: 1 standard atmosphere (atm) = 14.696 pounds per square inch (psi). Pressure conversion relationships: 1 bar = 10^5 Pascals; 1 dyn/cm² = 0.1 Pascals. 1 Torr = 133.322 Pascals; 1 mmHg = 133.322 Pascals. 1 mmH2O = 9.80665 Pascals. 1 engineering atmosphere = 98.0665 kPa. 1 kPa = 0.145 pounds per square inch (psi) = 0.0102 kilogram-force per square centimeter (kgf/cm²) = 0.0098 atmospheres (atm). 1 pound per square inch (psi) = 6.895 kPa = 0.0703 kilogram-force per square centimeter (kg/cm²) = 0.0689 bar = 0.068 atmospheres (atm). 1 physical atmosphere (atm) = 101.325 kPa = 14.696 pounds per square inch (psi) = 1.0333 bar. There are two systems for classifying valves: one is the “nominal pressure” system used in Germany (and also in China), which is based on the allowable operating pressure at normal temperatures (100 degrees in China and 120 degrees in Germany). One is the \"temperature-pressure system\" represented by the United States, which is based on the allowable operating pressure at a certain temperature. In the U.S. temperature-pressure system, except for 150LB which uses 260 degrees as the reference, all other levels use 454 degrees as the reference. For a 25-grade carbon steel valve rated at 150 pounds per square inch (150 psi = 1 MPa), the allowable stress at 260 degrees is 1 MPa; whereas at room temperature, the allowable stress is much higher, around 2.0 MPa. Therefore, generally speaking, the nominal pressure class corresponding to US standard 150LB is 2.0 MPa, that corresponding to 300LB is 5.0 MPa, and so on. Therefore, the nominal pressure and temperature-pressure class cannot be arbitrarily converted using pressure conversion formulas