I am pretty sure the US uses the international inch for far longer. Since before I started working with canadian companies in the 1990s. There is official looking documentation that shows the international yard (and thus the inch) defined in 1959 https://usma.org/wp-content/uploads/2015/06/sp447-app5.pdf?x40840 There are still various survey foot definitions with slightly different values in the US, and of course the nautical mile and related measures. https://oceanservice.noaa.gov/geodesy/international-foot.html
This rabbit hole is deep if you want to dive into it. On Thu, Sep 11, 2025 at 10:26 AM John Smith <[email protected]> wrote: > On Fri, 12 Sept 2025 at 02:18, Paul R Anderson <[email protected]> wrote: > >> Inches and millimeters have a conversion ratio where one value is >> approximately 1/29 the other. Specifically, 1 inch is equivalent to 25.4 >> millimeters. The approximation is not exact but is a common comparison for >> visual estimation. >> > > The inch was standardised to be exactly 25.4mm, except for the US, > although that changed in 2020 according to Wikipedia. > > > -- > You received this message because you are subscribed to the Google Groups > "weewx-user" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion visit > https://groups.google.com/d/msgid/weewx-user/CAGTinV4mAG387-k2eidpaZMDZ7i5OTh2diZHjcpHof0ZzqQsig%40mail.gmail.com > <https://groups.google.com/d/msgid/weewx-user/CAGTinV4mAG387-k2eidpaZMDZ7i5OTh2diZHjcpHof0ZzqQsig%40mail.gmail.com?utm_medium=email&utm_source=footer> > . > -- Peter Quinn (415)794-2264 -- You received this message because you are subscribed to the Google Groups "weewx-user" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion visit https://groups.google.com/d/msgid/weewx-user/CAA1SM2398Vpb8uLC3r_1PGfqG1KPEq5psGWA%2BtU-5tsamyx1eQ%40mail.gmail.com.
