: Does anybody know the mass of a black hole or where I could find the data

For a black hole forming from a collapsed star, it requires at least 1.4 solar masses to form a black hole. Anything less will form either a neutron star or a white dwarf (the fate of our sun).

Black holes evaporate under a process known as Hawking radiation, hence over a period of like 10^67 years, a black hole will shrink below the 1.4 solar mass limit (if not fed new matter). It doesn't stop being a black hole. It's event horizon just shrinks further and further. So in reality there is no lower limit to the mass of a black hole or it's size until it reaches atomic proportions.

Also, black holes in theory could be formed by super compression such as may have occurred during the early formation of the universe. No one has yet detected a black hole of less than "normal" size. Currently, black holes are inferred only by gravitational effects, not direct observation. Hence, any sub-mass black holes, if they are out there, would be hard to distinguish from a large planet or a brown dwarf.