My thermos holds about 40oz of coffee. I guzzle that fvcker every day. Mondays I often log in to work from home early, and then drive in to work a bit late (essentialy, work same hours, just commute later in the day so that way I have a bit of a head start in the AM.) So Mondays I'll drink a 12-20oz mug as well as my 40oz thermos. Friday I work from home, so have access to my coffee maker, often I'll drink between 4 and 6 12-20oz mugs worth of coffee. On Weekends I don't typically work, and usually I sleep later, but I still enjoy my delicious coffee, so usually Sat and Sun I drink about 2-3 12-20oz mugs of coffee.
Then, sometimes when I go out to lunch, I may drink some more coffee depending upon if the lunch destination has coffee.
On fridays or saturdays, or if I am on vacation, I also often have a cup of coffee after dinner, but, not on work days since I tend to stay up until 4 or 5 or sometimes 6 or 7 am. if I drink coffee late. (note: delayed sleep onset disorder. Even with no caffeine I only can force myself to sleep before like 2am with melatonin.)
Overall, I would say I average about 50oz of coffee per day.