@markwyner Oh, the US *does* use SI... just most people don't know it. The US are a member state of the BIPM (Bureau International des Poids et Mesures - International Bureau of Weights and Measures) which oversees the SI etc. And the US lab NIST, for example, plays/has played a large role in relation to the work of the BIPM.

Also, units such as the lb, are defined in terms of SI units e.g. 1lb = 0.45359237 kg. The SI is the only definitional system of units.

https://www.bipm.org/en/member-states