Well , there * usta be * mostly recognized guidelines . But buying / using tastes have changed over time .
5 inch , or close to it used to be Full Size . Compact used to be +/- 4 inch , with slightly shorter butt .
But nowadays , the previous Compact is now the norm for Duty Guns ( / Belt Guns ) .
Subcompact used to be +/- 3.5 inch , with butt chopping as much shorter than Compact , as Compact was shortened from Full Size .
Then with advances in material science and gun design , there were Really Small guns . And it became all jumbled what was Subcompact , and what was Micro .
* To Me * , l look at two criteria :
Is it small enough to be quasi plausable to fit in a normal pants pocket ?
Is it big enough to have a decent grip ( grasp) on the handle , such to be plausable as a " real gun " .
* For Me * , with my XXXL Hands , there are a buncha guns that fall into the no man's land gap . To where it's to big to pocket , but it's a hard to shoot well belt gun .