Calories per day to kilocalories per day conversion calculator above calculates how many kilocalories per day are in 'X' calories per day (where 'X' is the number of calories per day to convert to kilocalories per day). In order to convert a value from calories per day to kilocalories per day (from cal/d to kcal/d) type the number of cal/d to be converted to kcal/d and then click on the 'convert' button.