an average HD stream requires ~4mbit of bandwidth ( rounded numbers for ease of use) a 4k stream around 23mbit.
Let's say you have a 25 mbit connection, your maximum would be 3 stream; because you still require bandwith for you other devices besides in your home. Plus approaching the maximum margin puts a strain on your picture quality.
The above is a simplification as a lot more variables can come into play.
TLDR : it all depends on your bandwidth capabilities