 It is given by

where is Newton's gravitational constant and is the speed of light.For the electron,

so

Thus, if we ignore the electric charge and angular momentum of the electron, and naively apply general relativity on this very small length scale without taking quantum theory into account, a black hole of the electron's mass would have this radius.In reality, physicists expect quantum gravity effects to become significant even at much larger length scales, comparable to the Planck length

So, the above purely classical calculation cannot be trusted.