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