There is no theoretical upper limit to the mass of a black hole, but there is some evidence to suggest that there may be a practical limit. The largest known black holes have a mass of about 50 billion times that of the sun. Any larger, and it is possible that the black hole would become so massive that it would start to disrupt the accretion disk that feeds it. This would prevent the black hole from accreting any more mass, and it would eventually reach a maximum size.

However, it is also possible that there is no practical limit to the size of a black hole. If a black hole were to form in the early universe, when the density of matter was much higher, it could potentially grow to be much larger than any black hole that has been observed so far.

Ultimately, the question of whether or not there is an upper limit to the size of a black hole is still a matter of debate. More research is needed to fully understand how black holes grow and what limits their size.