Do You Really Need to Drink 8 Glasses of Water a Day?

Someone pouring a glass of water from a pitcher

How Much Water Do You Really Need?

Did you drink enough water today? Did you even notice? If you have a cup of coffee in the morning, half a bottle with your workout, and a few sips with meals, you’re probably running on empty. Now that you stop to check in with your body, you might even feel thirsty, Take a moment to go get a big, cool drink. And while you pour, think about it. What is your water goal, anyway?

Do You Need 8 Glasses of Water a Day?

8 glasses of 8 fluid ounces of water per day is the classic recommendation, and a great goal to set initially, but it’s definitely oversimplified. “Unfortunately, there has never been a landmark study on exactly how much water you should drink every day!” says Robin Foroutan, MS, RDN, HHC, and spokesperson for the Academy of Nutrition and Dietetics. “So even if it’s bunk, you have to start somewhere. Think of 8 glasses a day as the bare minimum, and then keep sipping.”  

In fact, the current recommendation from the Institute of Medicine is significantly higher, at least 2.7 liters of water per day for women, 3.7 liters for men, which translates to 11 to 15 cups of water per day. Some of that can come from hydrating foods and other beverages, such as watermelon and lettuce, or coffee and tea. But you still need a lot of water—and that’s just for “adequate” intake! So you might have to push those numbers higher, especially if you’re sweating hard during summer workouts.

“But it doesn’t really matter which calculation you use,” Foroutan confides. “They all boil down to that 8 to 12 glasses range.” What’s more important is how you feel. So track your intake for a few days. See how many glasses you’re getting. And in addition to the numbers, pay attention to your thirst and pee—if it’s darker than lemonade that’s a sign of dehydration.

Why Do You Need to Drink So Much Water?

Whatever your other health and fitness goals, drinking enough water can help you get there. Water is essential for your health and wellbeing, affecting every system in your body. It’s a natural detox, supporting your liver, kidneys, and bowel function. It powers athletic performance, clearing out lactic acid, so your muscles can do more. It helps you to focus and boosts your mood.

“If that doesn’t make you hit the bottle, maybe the promise of weight loss will?” says Foroutan. Water could also be the key to achieving your weight loss goals. Research shows those who bump up their H20 consumption by one to three glasses per day eat fewer total calories, as well as less saturated fat, sodium, and sugar. So the next time you feel hungry, start with a big glass of water, and see if you’re confusing your thirst and hunger cues.

How to Make Hydration Happen

Before you freak out about drinking upwards of a dozen glasses of water every day, size it up! When’s the last time you poured exactly 8 fluid ounces into a glass? That’s a pretty small tumbler. These days, a small to-go cup is 12 fluid ounces, a mason jar is 16 fluid ounces, a fancy water bottle is 17 fluid ounces, and an outdoorsy water bottle is 32 fluid ounces. So while your water goal might be higher than you realize, you can also fill up for success.

Check out the water logging feature in the Fitbit app, where you can edit your goal and log your water intake. It makes it easy, by giving you options to quickly add a glass or bottle of water. Then keep sipping! Whether that means carrying a pretty bottle all the time, letting a big pitcher chill in the fridge, or taking stretch breaks to swing by the office cooler. If you need a fresh twist, try different flavors of sparkling water or infusing what comes from the tap with lemon, cucumber, mint, strawberries, and more. There are so many ways to keep your cells happy and hydrated.

60 Comments   Join the Conversation

60 CommentsLeave a comment

  • Hello, my fit it Alta is keeping up to date with my water intake, can I include my big mugs of tea.

  • A good indicator is the color of your urine…dark yellow means you need more hydration, lighter color means you’re well hydrated. As well, if you are unusually tired, it’s a good idea to have a glass of water to see if a little more hydration is the ticket! Great post, thanks!

    • Crystal lite isn’t a very healthy choice.. Not much different then diet pop..
      Stick to reg water

    • Crystal lite not a healthy choice. Not much different then diet pop.
      I’d stick to reg water. You get use to drinking so much water after a few weeks.
      Washroom breaks will increase in the beginning but taper off as you get use to it..
      I drink 4l a day every day. Feel great!

    • I put instant no sugar tea in mine but just a little. Enough to take away the water
      Taste. I was told that it was ok so least I’m getting my water that way.

  • I am 86 years old, not over weight and have no health problems. I am not on any medication and walk my dog one hour every day.
    I have never drunk much water, even long days horse trekking, i.e. a cup of black tea at lunch.
    I now drink one glass in the morning, cup of tea at lunch and a glass of water with my evening meal plus two cups of coffee through the day, no afternoon tea.

  • But for heart conditions there is restricted fluid intake it can be somewhere between 700ml to 1.5 litres. Too much water consumption can damage the heart. The man in the hospital bed next to me has caused huge damage to his heart by overconsumption of water. He now needs bypass surgery because he has swollen his whole body by his pure water consumption.

  • Avoiding the formation of a kidney stone is another key reason for maintaining an intake of at least 2500ml water a day. This will help keep your urine levels diluted and reduce the chance of the crystals forming in your kidneys.
    The FitBit app really helps recording water intake but it could be improved if it logged the time as well as the volume.

  • Why is it measured in ounces (e.g. 8 fluid ounces) and yet the total amount required per day is in litres (e.g. 2.7 litres)? It’s not tricky maths, but consistency keeps things even simpler!

  • Hi,

    I have a hydratem8 bottle which I use daily, it makes me drink more although I use no added sugar squash as I can not drink plain water.

  • Confusing giving measurements in fluid ounces – most water bottles are now measured in litres, so how many litres of water should a man/woman drink per day?

  • This is way oversimplified – I hardly ever drink any ‘water’ (probably less than one glass every month) and I have no hydration issues. Tea, coffee, beer, juice, melon, lettuce, fruit,vegetables,soft drinks, even wine all contain water. Wine is approx. 12% alcohol, the other 88% is…. mainly water… beer is approx. 4% alcohol – 96% must be ….

    Of course you feel better when you are properly hydrated, urine colour is an easy check. Equally, choice of diet and lifestyle is a matter of personal choice, and of course body mass and activity levels factors.

    However, based on my ‘research’ (statistical sample of one which qualifies for most internet published research), the idea that you are doing something wrong if you don’t drink 2 litres of pure water, while not ‘bad advice’ is far too simple.

    There are many ways to stay fit and healthy…

  • For Europe (including the UK), you should include ml as well as fluid ounces. I presume you are quoting US fluid ounces which are not the same as imperial fl oz. Also, what kind of measure is a “glass” – glasses come in many different sizes (same comment for “cups”). I think ml ought to be the definitive measure here and it is good that the Fitbit app supports these various different measures.

  • Living in Sasebo, Japan, the summer weather is quite warm. I walk, on the average, 45 miles a week. My water intake is in excess of 200oz a day just in drinking water, not counting what I get from eating. The Japanese diet contains a lot of soups and liquids as well and of coarse, you can’t live in Japan without consuming a few glasses of green tea every day! It’s the law here! 😉 I was a bit overweight when I first came to Japan(250 pounds) and between the walking, the Japanese diet, and staying hydrated, I have gotten down to 165 pounds and have stayed at that weight for the past 4 years.

  • I was taught to take your body weight and divide that in half and that is how much water you need in a day. Eg., 120 lbs divided by 2 equals 60 ounces. I round up to 64 ounces which is 8 cups!

  • I drink a min. of 128 oz of water a day. Very easy to do. I have also lost weight and my workouts are far better. My most intake has been 197 oz.

  • I’ve always heard that coffee was dehydrating and that if drinking coffee, to be sure to drink more water????

    • Coffee is mostly water so no it’s not dehydrating.
      What people are trying to tell you is that caffeine is a diuretic (meaning it causes you to urinate more), but the effect of the water in your coffee far outweighs the effect of the caffeine.
      Therefore, a cup of coffee will hydrate you more than it dehydrates you, but it won’t hydrate you as well as plain water.

  • I drink almost 5-7 litres of water per day, I also do extensive walking (daily average 23k steps) n weights workout. Is intake of excess water is harmful for health especially the kidneys

  • So much conflicting advice exists for water intake, the best advice is to drink when thirsty as the vast majority of health care providers will recommend.

  • Hi I have a bottle from weight watchers and it gives y the time to start and restart have about three of them a day with juice can y let me know if that’s ok please thank u

    • You should read the article closer.

      Robin Foroutan, MS, RDN, HHC is a registered dietitian nutritionist specializing in Integrative Medicine.


    • The National Research Council, in 1945, suggested a daily intake of 2.5 L (approx. 64 oz) of water – much of which they thought was satisfied simply through *eating food*. Some researchers think more sedentary people in air-conditioned environs need half that, and again, food intake alone suffices. But as the nutritionist in the article points out, there has been no scientific study nailing down a minimum figure. She then proceeds to take a SWAG (scientific wild-a** guess) and suggest we drink… at least 64 oz daily.

      The most common sense approach is to drink when thirsty. When exercising or in the heat, pay particular attention to urine color and frequency. It’s rare to drink *too* much water, but going overboard can lead to electrolyte imbalances.

    • You’ve got to be really stupid to kill yourself by drinking too much water. Follow the recommendations and you’ll be fine, regardless of how much you get from food.

  • Best calculation I’ve every been given for how much water to drink per day is divide your weight by 2. That’s how many ounces you should drink. And for every ounce of caffeinated beverage that you drink add an ounce of water.

  • I am 67. For several years my legs itched and I scratched them so much you could see marks. After I started drinking water (32 ounce Yeti cup), at least 2/day, all of that itching disappeared. I’ve been good for a few years now. Last week I had to get a colonoscopy. I got dehydrated. My legs itched again. Water to the rescue!

  • I drink 36 ounces of tea before leaving the house. I put ginger, cardamon,cinommin, garden herbs, milk and honey. Sometimes just plain milk and coconut sugar.(I write so I sip while writing.) Do I need to drink water too?
    I’ll be peeing all day. (PLEASE DO NOT POST MY NAME)

    • I was hospitalized for 4 days this past year after passing out. When I came to I was unable to walk, had no feeling in my left arm, was confused and couldn’t speak. After ruling out a stroke or heart attack as well as other conditions it was determined that I had been drinking way too much water. I had depleted my body of sodium. I have had to cut back but am still confused as to how much I should drink. I drink about four large glasses of unsweetened green or black tea as well as a few of my 32 oz. bottle filled with water.

  • The natural process is to concerve fluid if there is a relative shortage of input. Hence dark urine merely shows you you are concerving. The dessert rat does not produce urine at all only crystals. The hyperboly about fluid in-put,is, as she states, unproven.

  • I there EveryOne!

    My name is keri and I’m like, soooo new to this Fitbit Alta and I’m sorta lost, and there’s things on here that I’m still not sure how, what everything is or what the program works, like,
    1) how to import how much water to import water,
    2)what the different programs are?
    I need to INFORM EVERYONE!
    Back in 2011, I had a stroke and with all the different medicines for Cronnic cordinary heart disease,
    I’m a little slow at understanding what people tell me to do.thats why I’m here asking for some
    ” HELP”!
    I’ve never ever tell people that I really don’t know my health story.
    Thank you again for reading this.
    Mrs.Keri Colburn

  • Can the articles include metric equivalent measurements please. The rest of the world outside the US uses the metric system. Thanks.

  • I drink many cups of herbal tea a day. Does this count as part of my water intake or should I be drinking 8+ cups of water as well?

    • I have found many articles on H2O in take for normal healthy person. However, with congested heart failure there is a tendency not to eliminate adequate amount of water and consequently can collect in the feet and ankles. Several articles end with the advice that the water intake should be monitored more closely but without advising how.

      Even with a “water pill’ it can be a problem not to let water collect. Apparently, there is a no available data on water consumption for someone with congested heart failure. My take is that, with a pill, it looks like if you can eliminate 2 liters of urine, then maybe the drinking intake should not be more than that. With sweat and breath vapor being the mechanism for a small deficit. Some where in the equation, the colon has more water in it than we think, a bad case of diarrhea, you can lose a few pounds of water quickly.

  • While in Massage Therapy school we discussed this topic and we’re told a good “rule of thumb” is half ounce of water per pound of body weight to keep properly hydrated.

  • Do vegans get more water in their diets making so they don’t have to drink as many glasses of water as recommended?

  • I have been drinking alkaline for 4 years now. My joints don’t hurt anymore. There are studies that say disease can’t live in an alkaline body. I believe that since I am 82 and only go to my doctor once a year for a check up. I drink 108 ozs a day. Two 20 oz glasses when I first wake up each morning.

  • It would be helpful if all your articles also state the metric measurements as most of the World is familiar with it.
    Otherwise very informative.

  • My goal for a number of years has been to “drink 1/2 my body weight in ounces” each day. This puts my target at 96 ounces per day minimum.

  • I am looking for a wrist band to wear that would change color when I or the wearer is getting dehydrated. The band would need to change color to show dehydration.
    I am looking for myself as I have a medical condition that has potential to cause dehydration. Also for my 100 year old mother who often is dehydrated and can’t remember to drink as you get older you loose the feeling of thirsty and can’t remember to do simple things like drink water. When she is dehydrated she is easily confused and dizzy, but also her confusion/out of it keeps she from thinking that she might need a drink of water.
    **the dehydration band can’t be tied to a smart phone as my mother is not able to operate the phone
    but for being 100 years old she does very well, she plays cards daily and swims in the pool and goes on day trips etc

    This type of dehydration band would be wonderful for older people as well as just Seniors and regular adults as most of the population in US is dehydrated a lot of the time
    Thank you so much
    If you could let me know where I might find such a thing I would be most appreciative

  • Should you drink water in sitting position? Is there any harm while drinking water in standing position?

  • What stupid article?
    You have
    Fluid ounces
    How can anyone work out what you are trying to say.

  • Can there be a reminder on the Ionic that reminds you to drink water throughout the day? (Just like there’s one for standing up/moving?) Thank you!

If you have questions about a Fitbit tracker, product availability, or the status of your order, contact our Support Team or search the Fitbit Community for answers.

Please note: Comments are moderated and may not appear immediately after submission.

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.