Nautical miles per day to feet per second conversion calculator shown above calculates how many feet per second are in 'X' nautical miles per day (where 'X' is the number of nautical miles per day to convert to feet per second). In order to convert a value from nautical miles per day to feet per second (from nmi/d to ft/s) type the number of nmi/d to be converted to ft/s and then click on the 'convert' button.