Newtons per square millimeter to megapascals conversion calculator above calculates how many megapascals are in 'X' newtons per square millimeter (where 'X' is the number of newtons per square millimeter to convert to megapascals). In order to convert a value from newtons per square millimeter to megapascals (from N/mm² to MPa) simply type the number of N/mm² to be converted to MPa and then click on the 'convert' button.