The distance from the
singularity of a
black hole out to the
event horizon, the surface within which
gravitation is so strong that not even
light can escape.
It is given by 2 M G / c2, so if you have a black hole of radius r, its mass is M = r c2 / 2 G. A black hole of radius 1 m is about 100 Earth masses. The temperature is inversely proportional to the mass and a one-gram black hole has a temperature of 1026 kelvins. It evaporates by Hawking radiation in 10-27 second.
G is of course the gravitational constant.