After the French Revolution, the French figured they needed to adopt the metric system because life wasn't hard enough. The French philosopher Marquis de Condorcet said the metric system was, "for all people for all time". He was correct, and America is the exception that proves the rule.
One of the bad things about metric conversion is, someone has to convert whatever it was you were using to the appropriate metric units and values. In a period without computers, the French came up with a very odd solution. The top hair dressers of the time had a noticeable lack of nobility to pamper, so they were enlisted to do these calculations. Hair dressers are notoriously bad at math and there were so many mistakes, Charles Babbage decided to make a machine to do the math.
The Difference Engine was so fabulously complex, it had 25,000 parts and weighed 15 tons. It was started in 1847 and finished in 1991. It took 9 more years to construct a printer for output. Just in time for the year 2000.