Hmmm I've never measured it, but we fill his bowl 3-4 times a day. We use a 4 cup measuring cup to fill his bowl, so I guess he drinks around 12 cups a day? That's a normal day. We noticed a long time ago he drinks more if he's stressed, like if we go to my parents for a weekend or something. At home he drinks in spurts and not a sip here or there. At my folks house he takes a drink every time he walks by his bowl.