You can have up to 50 breakout rooms and the capacity for each of those rooms is 200 participants.

More details can be found in this article.

Note: There is a way that the Zoom Team can create a maximum of 100 Breakout Rooms with a maximum capacity of 1000 per breakout room (depending on account limits), but if you decide to turn this on, participants may be required to update their Zoom client.

This switch would be flipped on for the entire Zoom account, not just for one individual user.

All participants would have to be on Zoom client version 5.2 or higher and anyone who wants to join and does not have the correct version would be required to update to join the meeting.

If users do not have administrative control of their computers, this will require assistance from your IT Department to update the client.

This is an important consideration when deciding whether to have this 100 Breakout Room option enabled.