Calculation page welcomes you on main screen. Just insert your hours into one of 24 fields. You dont have to go in order. You can write in any field you want. Calculator will take care of the Write your times without minute seperator :. 1h30mins is as 130. 45mins as 45. If you write some minutes above 60, it will be calculated in hours. For example if you write 70 in a field, it will be calculated as 1:10.