The reactions to your comment got me curious enough to check. The mug I use for coffee and tea holds almost exactly 400 mL when comfortably full and I used to drink 2 of those per day (across 12 hours or so). Based on that, personally I'd consider ~800 mL of black coffee to be on the high end of moderate consumption.

Yeah, people think 400-500ml is a lot for some reason, but it’s not a abnormal coffee mug size at all. The Ember mug I have is around 430ml.