Miles per hour to nautical miles per day converter on this page calculates how many nautical miles per day are in 'X' miles per hour (where 'X' is the number of miles per hour to convert to nautical miles per day). In order to convert a value from miles per hour to nautical miles per day (from mph to nmi/d) type the number of mph to be converted to nmi/d and then click on the 'convert' button.