more than 500 to 600 milligrams (the equivalent of 5 to 7 cups of coffee) a day.
1,000 ml = 1 liter, or just over a quart.
500 ml = 2.1 cups. And that's 8oz for a standard cup. Standard Starbucks "cups" are at least twice that.
Some MD or expert right there. The internet is the gospel I tell ya.