As with everything else, it depends.
I recommend starting with half your body weight in ounces, but not to exceed 80 ounces per day – unless needed. That’s a starting point.
To clarify the ‘it depends’ and the ‘unless needed’, some common sense must be applied.
There isn’t one rule that fits everyone, just as there is no ‘one best diet’.
If you’re highly active, you might need more. If you weigh 150 pounds and you’re drinking 75 ounces per day, but peeing non-stop, you might want to tone it down a bit.
‘Drink when you’re thirsty’ is a good rule of thumb. Where most people get confused is, they mix up thirst for hunger. (In other words, often times when you think you’re hungry, you may just be thirsty.)
Then there’s the matter of the quality of your water. On this subject, I am not an expert. However, I do put electrolytes in all of my water because our bodies need minerals for optimal function.
My basic understanding of water quality is that there’s a wide spectrum, ranging from Poland Spring (bottled tap water in harmful plastic) all the way to actual spring water that you could charge using rock gardens, the sun, and the moon (which you’re not going to do).
Going back to the quantity of water, how much you should drink:
Caffeinated drinks are dehydrating, so, no, they do not count towards your total water for the day.
Neither does anything else that’s not water, such as anything with added sweeteners of ANY kind.
Sparkling water, unsweetened – yes, that counts.
This advice is what has worked for me and the ~100 or so clients I’ve provided health coaching to.
I am always open to others’ opinions and would love to hear yours below.
Matt Fried 