Millipascals to pounds per square inch conversion calculator shown above calculates how many pounds per square inch are in 'X' millipascals (where 'X' is the number of millipascals to convert to pounds per square inch). In order to convert a value from millipascals to pounds per square inch (from mPa to psi) type the number of mPa to be converted to psi and then click on the 'convert' button.