If you hit google you'll see it's less coffee as such and more total caffeine. And that's around 400mg a day. Then you'll need to know how much is in those cups you wanna drink
I don't drink coffee and would prefer my clients not drink it all BUT i get that people like coffee and it is a habit they have developed over the years so i tell my clients 1 cup of coffee plain in the morning is acceptable. no coffee allowed after noon