I'm probably the last geek on earth to discover that the model numbers of 3V CR button cell batteries describe their size. E.g., a CR2032 is 20mm diameter and 3.2mm thick. But if I wasn't, now you are.
— matt blaze (@mattblaze) July 17, 2018
Blaze, it turns out, was not the last geek to find this out: I didn’t know it either. I’m betting neither did a bunch of you so I’m sharing the knowledge.