> I do wonder if you do like, size estimates of a black hole in my room. Suppose I have a black hole in my room, I'd be curious to know what the mass of that is, like a fun fact, tidbit somewhere.

Forgot to answer this first!

Basically, ~1 cm radius black hole has the mass of the Earth – really, Earth would need to get this small to become a black hole. I've made a very simple demo for a kids lecture I gave recently, https://plav.in/outreach_demos/squeeze-earth-v2.html. Also see https://xkcd.com/1680/ of course :)