to be honest, probably only about 3 - 4. i don't believe that everybody in the world benefits from the "gallon a day" thing. if i drink too much water in the day, i feel heavy, lethargic, & groggy. even spacing large amounts of water throughout the day, by the end of the day, i feel like i'm carrying around a dump truck in my tummy. i know i need to drink a bit more, since i take spirulina every morning.