Two Methods: Calculator Online. Learn how to Convert MPa to psi. A MPa (megapascal) is a unit of measurement for pressure. A single pascal (Pa) is a unit of pressure equal to one newton per square meter. Mega means million, therefore one MegaPascal equals 1,000,000 Pascals. You can convert an MPa value to psi(pound-force per square inch) by using a calculator or you can use an online unit conversion calculator.