Calories per day to BTU (IT) per hour converter on this page calculates how many BTU (IT) per hour are in 'X' calories per day (where 'X' is the number of calories per day to convert to BTU (IT) per hour). In order to convert a value from calories per day to BTU (IT) per hour (from cal/d to BTU/h) type the number of cal/d to be converted to BTU/h and then click on the 'convert' button.