How much water should you drink per day?

All also depends on your size, physical activity, and overall health. An easy way to know if your drinking enough is to look at your urine. Urine should be a pale light yellow color. If the color is dark yellow the odds are your dehydrated and should drink more.
"8 glasses a day" is an urban myth. It's true that the RDA is 2 liters of water per day. But this includes the water in the food that you eat. The water in food is significant: For instance, apples are 85% water. If the rest of your diet was flour, butter and chocolate, then you would need 8 glasses a day; but it's not, so 8 glasses is more than you need.