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