Question

What defines a black holes size?

Answer 1

The size of a black hole is defined in terms of its mass.

Explanation:

The size of a black hole is defined by the Schwarzschild radius:
`r = (2GM)/c^2`
Where `G` is the gravitational constant, `M` is the mass of the black hole and `c` is the speed of light.

If the black hole is spinning or has an electric charge it can alter this size by up to a factor of 2 by more complex equations.