At least the whole EU uses SI units by Directive 80&#x2F;181&#x2F;EEC (so called &quot;Units of Measure Directive&quot;). From everything I know, most other countries of the world use SI as well. Not surprising, as the system is now 55 years old and explicitly replaced former definitions.<p>Even US laws explicitly refer to SI, for example the Metric Conversion Act of 1975: <a href="http:&#x2F;&#x2F;www.gpo.gov&#x2F;fdsys&#x2F;pkg&#x2F;STATUTE-89&#x2F;pdf&#x2F;STATUTE-89-Pg1007.pdf" rel="nofollow">http:&#x2F;&#x2F;www.gpo.gov&#x2F;fdsys&#x2F;pkg&#x2F;STATUTE-89&#x2F;pdf&#x2F;STATUTE-89-Pg100...</a>