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