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Like most people you probably have heard that you’re supposed to drink 8 8-ounce glasses of water a day. That number, totaling 64 ounces, has been drilled into the psyches of people in the US and other places, but it turns out that how much water to drink in a day is more complicated than that. So here’s how to figure out the real number of ounces to drink because it actually varies from person to person.

3 glasses of water in the sun
Via: Jana Sabeth/Unsplash

How much water you need will change depending on your climate and your job for starters. Someone doing manual labor in the sun will sweat more and will need more fluid overall. Someone in this situation might benefit from drinking cow’s milk or coconut water since both have some salt and small amounts of sugar which help to hydrate human bodies more efficiently than plain water. Experts say that the average person doesn’t need sports drinks even on a hot day and that all that sugar isn’t good for us.

But, beyond occupation and temperature the single most important factor for how much water to drink is your weight. Those with a higher weight will often need more water. It makes sense when you think about it.

person standing on a scale
Via: i yunmai/Unsplash

The best way to determine how much water to drink is to take your weight and divide it by two. That is the number of ounces you should aim for everyday. Someone with a body weight of 128 pounds will most likely need 64 ounces but people who weigh more or less than that will require different amounts.

A 1945 guide created by the Food and Nutrition Board of the National Research Council suggested 2.5 liters of water a day for adults and that was including from any tea, coffee, soup, and other foods you ingest.

And, yes, you can absolutely drink too much water. That problem is called water intoxication. When there is too much fluid in the body our cells swell up. The cells of the brain also swell causing confusion and neurological symptoms. High blood pressure, low heart rate, and hyponatremia are a few of the conditions that can occur with water intoxication.

water coming out of the tap too fast
Via: Jacek Dylag/Unsplash

In severe cases it can be fatal, but drinking small amounts of fluid often and using the toilet regularly will ensure this doesn’t happen.

The bottom line is don’t force down water if you’re truly not thirsty and likewise don’t assume you’re getting enough water just because you had 8 glasses of the stuff. Incidentally, the 8 glasses thing isn’t actually founded in science and is closer to an old wives tale than a true guideline for hydration. Doctors and nutritionists remain stumped on where the 8 glasses number comes from and some maintain that, contrary to public fear, “We are not all walking around in a state of dehydration.”