You say millimetre; I say millimeter, let’s call the whole thing off!
Why on earth does the United States of America still use the imperial system?
We want the USA to be exceptional but not in this sense.
On Metric-Conversions.org we find this Definition: “The millimetre is a unit of length in the metric system, equivalent to one thousandth of a metre.” In terms of worldwide use of the metric system this is said, “The millimetre, as part of the metric system, is used as a measure of length across the globe. The most notable exception is the United States, where the imperial system is still used for most purposes.”
And “The metric system originated in France in 1799 following the French Revolution although decimal units had been used in many other countries and cultures previously. Although there have been many different measurements and the definitions of the units have been revised, the official system of measurements of most countries is the modern form of the metric system which is known as the “International System of Units“.
The USA was planning to adopt the metric system in the 1970s. What happened? The matter of fact is metric is base ten. There we go, not so hard.
The “American” method of thinking about the metric system is overcomplicated. We do not need people to think about “converting” from inches to centimeters, celsius to fahrenheit, or quarts to litres. If we just use the metric system, we do not have to convert!
Our recommendation: Use metric.