Millijoules to kilowatt hours conversion calculator above calculates how many kilowatt hours are in 'X' millijoules (where 'X' is the number of millijoules to convert to kilowatt hours). In order to convert a value from millijoules to kilowatt hours (from mJ to kWh) simply type the number of mJ to be converted to kWh and then click on the 'convert' button.