Feet per minute to millimeters per second conversion calculator above calculates how many millimeters per second are in 'X' feet per minute (where 'X' is the number of feet per minute to convert to millimeters per second). In order to convert a value from feet per minute to millimeters per second (from ft/min to mm/s) simply type the number of ft/min to be converted to mm/s and then click on the 'convert' button.