The number of glasses of water contained in one litre varies according on the size of the glass. An 8-ounce glass is equivalent to little less than 1/4 of a litre, so slightly more than four 8-ounce glasses of water equals 1 litre.
If the glass is measured in cups, 3 litres of water equals approximately 13 cups. This indicates that 1 litre equals approximately four and one-third cups of water. It would take around six 6-ounce glasses of water to equal 1 litre, or two 16-ounce bottles of water to equal 1 litre.