Hydration Calculator: How Much Water Do You Need to Drink a Day?

Good hydration can improve your mood, sleep, and overall health and wellness. Find out if your water intake is adequate by using this simple tool.

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woman in corner window drinking water
It's important to drink enough water every day, but fluid from water-rich foods will help you hit your hydration goal.Valentina Barreto /Stocksy

Calculating the amount of water you need to drink daily is more complicated than you may think. That’s because hydration needs are far from one-size-fits-all.

In general, the National Academies of Sciences, Engineering, and Medicine suggest that each day women get a total of about 2.7 liters (L), or 11 cups, of fluid and men get about 3.7 L (16 cups). Not all of that fluid has to be water intake. Whole, nutrient-rich foods and beverages, including the following, also count toward your fluid intake:

On the other hand, alcohol is dehydrating and does not count as fluid. Soda counts but is not a healthy choice.

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Find Out How Much Water You Need to Drink per Day

To give yourself a better sense of how much water you need to drink each day, use this hydration calculator.


What Factors Affect Fluid Needs?

Various factors can increase or decrease the amount of fluid your body needs to function at its best.

Birth Sex

Compared with people born female, those born male generally need more fluid to support their increased body mass, lower average body fat, and increased calorie burn each day.

Body Weight

Hydration needs are influenced by the surface area of the body, metabolic rate, and body weight, per a paper published in the July 2016 Annals of Family Medicine. As a result, as body weight increases, fluid needs increase as well, notes the University of Missouri System.

Life Stage

Similarly, when someone is pregnant, they require additional fluids to maintain amniotic fluid levels and keep the baby growing steadily, as PennState discusses. If you're nursing a growing baby, you’ll need to drink more fluids so that your body can make enough milk, according to the Academy of Nutrition and Dietetics.

Diet Quality

As the Mayo Clinic points out, the foods you eat will also affect your hydration and the amount of fluid you’ll need to drink. For example, if you get ample fruits and veggies each day (both of which are packed with hydrating fluid), you won’t need to gulp down as much water.

Soup is another food that is fluid-rich and can help you meet your target water intake.

If you eat a lot of these foods each day, you won’t need to drink quite as much. But if your fruit and vegetable intake is low on any given day, a few extra glasses of water will compensate for the fluid you’ll miss.

Activity Level

When you sweat during exercise or on a hot summer day, you’ll need to replace the fluids you’ve lost by drinking more H2O. As the American College of Sports Medicine points out, the intensity and duration of exercise affects how much you sweat and your subsequent fluid needs. According to a study published in Sports Medicine in March 2017, genetics and how accustomed you are to a given climate can also influence sweat volume.

Unfortunately, calculating exact hydration losses from physical activity is complicated, because people sweat at drastically different rates, according to the American College of Sports Medicine. In other words, even in the exact same conditions, two people of the same gender, weight, and with similar diets will sweat differently — and thus need different amounts of fluid.

RELATED: 6 Unusual Signs of Dehydration

The Importance of Staying Hydrated

While water intake needs vary, one thing is for sure: Meeting your personal hydration needs each day will have a tremendous benefit to your health.

Indeed, as the Harvard School of Public Health points out, good hydration keeps the body functioning properly, lubricates joints, and regulates body temperature. The university also notes that good hydration helps you sleep better, think more clearly, and even puts you in a better mood!

One Last Thing: Don’t Flood Your System All at Once

Drinking water gradually throughout the day is important. Too much water at one time may increase the risk of a condition called hyponatremia, which occurs when the electrolytes in the body become depleted. As the Mayo Clinic states, hyponatremia may be life-threatening.