What do you feel is the likely range of black holes in the universe, from smallest to largest? Boy, that's a lovely question. The smallest black hole - I suspect [can] be made from the collapse of a neutron star that picks up some matter and by picking up this matter becomes more massive than the critical amount and collapses. I'm afraid I'm not being as imaginative as I could be in thinking of a way to get small black hole, but a mass of the a neutron star which is maybe two times the mass of the sun. And what's the biggest one. Well, how big would such a thing be? Well such a thing, a black hole would be about that big.