From Singularity to Spaghettification:

Black holes are some of the most peculiar phenomena that exist in the universe. According to mathematical principles, any object that has mass can become a black hole. This means that any object, including humans, can become a black hole if their mass is condensed to a small enough space. This area is called the Schwarzschild Radius, which is the radius at which the object becomes so dense that nothing, not even light, can escape its gravitational pull. If an individual wanted to transform themselves into a black hole, they would need to condense all of the matter that makes up their body into an area that is one sextillion times smaller than a grain of sand. However, the more mass that gets compressed into a black hole, the stranger the effect can be.

For instance, if a Boeing 777 jet suddenly transformed into a black hole, its entire mass would be compressed into an area with a tiny radius of 3.386^-22 meters. This black hole would be incredibly small, and it would not last very long due to the effects of Hawking Radiation, which would cause the black hole to evaporate away in just one second. At this point, the entire mass of the black hole would be converted into an enormous amount of energy equal to five million megatons of TNT, which is 87,000 times more powerful than the most powerful nuclear bomb ever detonated. This energy would be enough to obliterate the entire planet.

If an individual wanted to transform Mount Everest into a black hole, they would need to condense the entire mountain into a space that is smaller than a nanometer. To put this in perspective, this space would be just one-billionth of a meter in length or the size of ten helium atoms placed side by side. If an individual wanted to transform the Earth into a black hole, they would need to compress the entire planet into a space that is the size of a single U.S. penny.

Once a black hole forms, it can continue to grow in size by absorbing additional matter, such as gas and dust from its surroundings, and on occasion, entire stars and solar systems. Black holes can even consume other, smaller black holes to rapidly increase in size and ferocity. For example, the black hole XTE J1650-500, which is believed to be the smallest black hole ever discovered, has a radius of just twelve kilometers and contains the mass of between five to ten Suns inside of it. In comparison, the black hole GCIRS 13E is roughly the size of the continent of Europe and contains the mass of 1,300 Suns inside of it.

There are still far larger black holes lurking in space. For instance, HLX-1 is designated as an intermediate-sized black hole. It has a radius of 295,300 kilometers, which is roughly as wide as four Jupiters placed side by side, and it contains the mind-boggling mass of 100,000 Suns inside of it. In the center of the Milky Way galaxy lies a supermassive black hole known as Sagittarius A, which has a huge radius of 12,700,000 kilometers, about five percent of the distance between Earth and Venus, and contains the ridiculous mass of 4,300,000 Suns inside of it.

However, the largest known black hole in the entire universe is the Ultramassive Class black hole, which is sometimes classed into an entirely separate category. The Ultramassive Class black hole has a radius that is 1,600 times greater than the distance between Earth and the Sun and contains the mass of forty billion Suns. To put that into perspective, it is the mass of forty billion times the size of the Sun.