You can download the breakspeed app and use it on matches on youtube to find out. It will differ a lot based on which game, how they rack and which rules they are using. An guesstimate is 9 ball: 17-21 from the side rail and maybe a bit harder from the middle with matchrooms new rules. 10 and 8 ball: 19-24. I think most pros can control a break at 20-21 mph, fast breakers can control 23. Above 23 most pros are probably losing control of the CB more than not.