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Water intake calculator: how much to drink

Short answer

The US National Academies set an adequate intake of about 3.7 L of total water a day for men and 2.7 L for women, counting water from food. About 3.0 L and 2.2 L of that comes from drinks of all kinds. Exercise adds whatever you sweat out: weigh yourself before and after a session to find your own sweat rate.

Last reviewed 28 October 20262 published sourcesNot medical advice

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Water intake calculator

Daily reference intake, plus sweat loss from a workout if you weighed in.

Units
Add a workout

Total water a day

3.7 L

Drinks and food

From drinks

3.0 L

Any drink counts

These are the Institute of Medicine's adequate intakes for healthy adults. Needs rise with heat and exercise.

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Daily reference intakes

The Institute of Medicine set adequate intakes for total water, from drinks and food together, based on the median intake of healthy people in US survey data (Institute of Medicine, 2005 (water)). Most healthy people meet their daily needs by letting thirst guide them, and needs go up in hot weather and with physical activity.

Adequate intake of water per day, adults 19 and over
GroupTotal waterFrom drinks
Men 19+3.7 L (125 fl oz)3.0 L (101 fl oz)
Women 19+2.7 L (91 fl oz)2.2 L (74 fl oz)
Pregnancy3.0 L (101 fl oz)2.3 L (78 fl oz)
Breastfeeding3.8 L (128 fl oz)3.1 L (105 fl oz)
Institute of Medicine (2005). Total water includes water in food. US fluid ounces.

Your sweat rate

The ACSM's method: sweat loss = body weight before − body weight after + fluid drunk − urine passed, divided by exercise time (Sawka et al., 2007 (ACSM)). One kilogram of weight lost is about one litre of sweat.

For example, starting at 70 kg, finishing at 69.2 kg and drinking 0.5 L during a one-hour session gives a sweat rate of 1.3 L an hour and a net loss of 1.1% of body weight, inside the ACSM's 2% guide.

Training late in the day? Caffeine also affects sleep, so check the caffeine cutoff calculator. For calories, see the TDEE calculator.

Log water from your Home Screen

Tap the Reps widget to log a drink. Your total updates straight away, follows your saved presets and units, and is saved to Apple Health.

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Common questions

How much water should I drink a day?

The Institute of Medicine's adequate intake for adults is 3.7 L of total water a day for men and 2.7 L for women, of which about 3.0 L and 2.2 L typically come from drinks; the rest comes from food. These are typical intakes of healthy people, not minimums, and needs rise with heat and exercise.

Do coffee and tea count toward water intake?

Yes. The drinks figure in the reference intake includes all beverages, not only plain water. Food supplies roughly a fifth of total water on average.

How much should I drink during exercise?

Sweat rates vary widely, so the American College of Sports Medicine recommends weighing yourself before and after exercise to learn your own losses, and drinking enough to avoid losing more than 2% of body weight. Avoid drinking so much that you gain weight during exercise.

Sources

Figures on this page were checked against these publications on 28 October 2026.

  1. Institute of Medicine. Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate. Chapter 4: Water. Washington, DC: The National Academies Press; 2005. doi.org/10.17226/10925
  2. Sawka MN, Burke LM, Eichner ER, Maughan RJ, Montain SJ, Stachenfeld NS. American College of Sports Medicine position stand: exercise and fluid replacement. Medicine & Science in Sports & Exercise. 2007;39(2):377–390. doi.org/10.1249/mss.0b013e31802ca597

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