The Imperial system is outdated and provides a convoluted approach to measuring everything from mass and volume to temperature.
There is an entire set of prefixes used for different factors of ten that can be used to convert metric measurements, but they always have the same base unit value and convert by a power of 10.
One millimeter will always be 1/1000 of a meter just as one milligram will always be 1/1000 of a gram simply because the added prefix "milli" converts the value to a unit consistently proportional to the original. In comparison, 1 mile is 5280 feet, 1 foot is 12 inches, and 1 yard is 3 feet. There is no logic behind such a system.
A plan to incrementally convert the US to the more logical metric system can be implemented. It is time to upgrade with the rest of the world