I think I know what you mean, and I can answer this with quite a bit of experience.....
It depends :-) It depends on the tank manufacturer, even when considering the "exact" same standard size tank, like a 40 gallon breeder, for example. I've had a ton of tanks over the years, and built several stands, and this dimension varies for sure. If you're building a stand or considering a specific space or custom install, I would personally figure out how to put my own tape measure on the trim.