Inches of mercury to hectopascals conversion calculator shown above calculates how many hectopascals are in 'X' inches of mercury (where 'X' is the number of inches of mercury to convert to hectopascals). In order to convert a value from inches of mercury to hectopascals (from inHg to hPa) just type the number of inHg to be converted to hPa and then click on the 'convert' button.