--- title: The Amount of Water You Actually Need Per Day description: Should you drink 8 glasses of water a day? How much water you should drink for performance and to avoid dehydration depends on the person canonical: https://time.com/4048173/water-drinking-tips/ author: TIME article:opinion: false article:content_tier: free article:published_time: 2015-09-25T14:19:51.000Z article:modified_time: 2026-02-22T11:14:07.080Z article:section: Health og:title: The Amount of Water You Actually Need Per Day og:description: Hint: it's not always eight glasses og:url: https://time.com/4048173/water-drinking-tips/ og:site_name: TIME og:image: https://static.time.com/v3/assets/bltea6093859af6183b/blt0a2427ec9113da54/6988652e196cf41f1f0382ea/water-bottle.jpg?branch=production&width=3840&quality=75&auto=webp&crop=16:9 og:image:width: 1200 og:image:height: 675 og:image:alt: water-bottle og:type: article twitter:card: summary_large_image twitter:title: The Amount of Water You Actually Need Per Day twitter:description: Hint: it's not always eight glasses twitter:image: https://static.time.com/v3/assets/bltea6093859af6183b/blt0a2427ec9113da54/6988652e196cf41f1f0382ea/water-bottle.jpg?branch=production&width=3840&quality=75&auto=webp&crop=16:9 ---  # The Amount of Water You Actually Need Per Day ## Video: Should I Drink Seltzer Water? [Watch (HLS stream): Should I Drink Seltzer Water?](https://cdn.jwplayer.com/manifests/SSdTN2EQ.m3u8) (1:30)  _Published 2015-02-04. Seltzer -- also known as bubbly water, carbonated water, soda water and sparkling water -- comes with as many health myths as it does names. Luckily, seltzer is one of the rare instances where something you love drinking isn’t bad for you._ by [Julie Mazziotta / Health.com](https://time.com/author/health-com/) ## Julie Mazziotta / Health.com Sep 25, 2015 2:19 PM UTC  Bottle of water Bottle of waterGetty Images by [Julie Mazziotta / Health.com](https://time.com/author/health-com/) ## Julie Mazziotta / Health.com Sep 25, 2015 2:19 PM UTC Eight, 8 oz. glasses of water a day: it’s a [rule that’s been burned into our brains](http://www.health.com/health/article/0,,20824599,00.html) for years as the ideal amount of fluid to drink each day. Yet no matter how many [times](http://www.foxnews.com/story/2007/12/24/seven-medical-myths-even-doctors-believe.html) [experts](http://www.nytimes.com/2015/08/25/upshot/no-you-do-not-have-to-drink-8-glasses-of-water-a-day.html) say that’s[ not quite accurate](http://www.health.com/health/article/0,,20824599,00.html), many still believe “8×8” is the magic amount. The truth: How much water you should drink each day really, truly depends on the person, Robert A. Huggins, Ph.D., of the University of Connecticut explained to _Health_. “Fluid needs are dynamic and need to be individualized from person to person. Factors such as sex, environmental conditions, level of heat acclimatization, exercise or work intensity, age, and even diet need to be considered.” What this means is that simply listening to your thirst is the best way to gauge when to drink. Another way to monitor hydration is to look at your pee before you flush. You want it to look like [lemonade](http://www.health.com/health/article/0,,20824599,00.html); if it’s darker than that, you should down a glass. **But what about exercise?** To gauge how much water you specifically should take in during exercise, Huggins recommends doing a small experiment on yourself. First, before you work out weigh yourself wearing with little to no clothing. “If you can, \[make sure you’re hydrated beforehand\] and avoid drinking while you exercise to make the math easy,” Huggins says. But if you get thirsty, don’t ignore it: drink some and make sure to measure the amount. After you’re done exercising, weigh yourself again. Then, take your first weight and subtract the second weight, and you’ll end up with how much fluid you lost. Convert this to kilograms (if you search it, Google will return the number for you or try a [metric converter](http://www.metric-conversions.org/weight/pounds-to-kilograms.htm)), then drink that amount in liters. (If you drank some water during exercise, subtract the amount of water you drank from your final total.) This is your “sweat rate,” Huggins says. It’s the amount of water you should drink during or after your next workout to replace what you’ve lost. (You can also use an [online calculator for sweat rate](http://www.triharder.com/thm%5Fswrate.aspx); just plug in your numbers.) Complicated much? We agree. Huggins estimates that most people lose between one to two liters of sweat for each hour of moderate intensity exercise. But ultimately thirst should still be your guide. **Why it’s important to get the right amount** You already know that dehydration can be dangerous, but over-hydrating may actually be just as bad. In fact, a new consensus report in the _British Journal of Sports Medicine_ found that many athletes are at risk of [exercise-associated hyponatremia](http://bjsm.bmj.com/content/early/2015/07/14/bjsports-2015-095004.short?rss=1), which is an electrolyte imbalance that can be caused by drinking too much liquid. This can lead to nausea and vomiting, headaches, fatigue, and in serious cases, coma and even death. While it was previously thought to only be a concern for long-distance athletes competing in events like marathons and Ironmans, the paper (which was funded by CrossFit, Inc.) concluded that many athletes are actually dangerously over-drinking during events as short as 10K races and even bikram yoga classes, Tamara Hew-Butler, Ph.D., lead author of the paper, explained to _Health._ Because “it is impossible to recommend a generalized range especially during exercise when conditions are dynamic and changing, there is not one size that fits all!” she adds. So the best method to keep you in that sweet spot between over- and under-hydrated is, as with many things, to listen to your body. [_This article originally appeared on Health.com_](http://news.health.com/2015/09/16/the-amount-of-water-you-actually-need-per-day/?xid=time) _More from Health.com:_ * [7 Easy Ways to Drink More Water](http://www.health.com/health/video/0,,20836567,00.html?xid=time) * [12 Reasons Why Dehydration Is Bad for Your Body](http://www.health.com/health/gallery/0,,20924876,00.html?xid=time) * [Fat Water Is Now a Thing](http://news.health.com/2015/08/07/fat-water-is-now-a-thing/?xid=time) ```json [{"@context":"https://schema.org","@type":"NewsArticle","@id":"https://time.com/4048173/water-drinking-tips/","mainEntityOfPage":{"@type":"WebPage","@id":"https://time.com/4048173/water-drinking-tips/"},"headline":"The Amount of Water You Actually Need Per Day","datePublished":"2015-09-25T14:19:51.000Z","dateModified":"2026-02-22T11:14:07.080Z","description":"Hint: it's not always eight glasses","url":"https://time.com/4048173/water-drinking-tips/","keywords":["Public Health","Water"],"thumbnailUrl":"https://static.time.com/v3/assets/bltea6093859af6183b/blt0a2427ec9113da54/6988652e196cf41f1f0382ea/water-bottle.jpg?branch=production&width=1200&quality=75&auto=webp&crop=1200:675&height=675","author":[{"@type":"Person","name":"Julie Mazziotta / Health.com"}],"articleSection":"Health","image":[{"@type":"ImageObject","url":"https://static.time.com/v3/assets/bltea6093859af6183b/blt0a2427ec9113da54/6988652e196cf41f1f0382ea/water-bottle.jpg?branch=production&width=1200&quality=75&auto=webp&crop=1200:675&height=675","width":1200,"height":675,"headline":"water-bottle","caption":"water-bottle","creditText":"Getty Images","representativeOfPage":true}],"publisher":{"@type":"Organization","name":"Time","url":"https://time.com/","logo":{"@type":"ImageObject","url":"https://time.com/images/logo.png","width":528,"height":156},"foundingDate":"March 3, 1923","sameAs":["https://www.facebook.com/time","https://www.instagram.com/time/?hl=en","https://twitter.com/time","https://www.pinterest.com/timemagazine"]}},{"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"item":{"@id":"/section/health/","name":"Health"}},{"@type":"ListItem","position":2,"item":{"@id":"/tag/public-health/","name":"Public Health"}},{"@type":"ListItem","position":3,"item":{"@id":"https://time.com/4048173/water-drinking-tips/","name":"The Amount of Water You Actually Need Per Day"}}]},{"@context":"https://schema.org","@type":"VideoObject","name":"Should I Drink Seltzer Water?","description":"Seltzer -- also known as bubbly water, carbonated water, soda water and sparkling water -- comes with as many health myths as it does names. 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