The "size" of a black hold is directly proportional to its mass. Specifically: Mass * 2 * The Gravitational Constant / The Speed of Light Squared: https://en.wi

The "size" of a black hold is directly proportional to its mass. Specifically: Mass * 2 * The Gravitational Constant / The Speed of Light Squared: https://en.wikipedia.org/wiki/Schwarzschild_radius https://en.wikipedia.org/wiki/Schwarzschild_radius Note that the speed of light squared is a really big number, so black holes are quite small relative to their mass.