Depending on what wifi you use (open wifi/local wifi/global wifi/free wifi/1G/2G/3G/4G/Airport Wifi/Company Wifi)
Each wifi can take a certain amount of users on it before it starts to slow down. That also depends on your computer but mostly just on the wifi. Things that eat a lot of wifi are Instagram, Facebook, YouTube & Twitter. Also things like forums, download webs & video sharing websites eat a lot of wifi when some one uses it.
Open Wifi = Guessed Max. 40 Users Before It Starts To Deny Other Wifi Requests.
Local Wifi = Guessed Max. 14 Users Before It Starts To Deny Other Wifi Requests.
Global Wifi = Guessed Max. 50.000.000 Users Before It Starts To Deny Other Wifi Requests. (Mostly Doesn't Deny Anything)
Free Wifi = Guessed Max. 7 Users Before It Starts To Deny Other Wifi Requests.
Airport Wifi = Guessed Max. 32 Users Before It Starts To Deny Other Wifi Requests.
Company Wifi = Depends On Company. (I prefer Ziggo)