Water intake calculator
Estimate how much water to drink per day from the National Academies reference values for total water, with an allowance for exercise. Results in liters and cups.
How the estimate is built
The National Academies' adequate intake for total water (from drinks and food combined) is about 3.7 liters a day for adult men and 2.7 liters for adult women. Food usually supplies around a fifth of that, so the drink share is roughly 3.0 L and 2.2 L. For exercise, this calculator adds about 0.5 liters per hour, a middle-of-the-road figure; sweat rates vary widely, from under half a liter to more than two liters an hour.
total water AI: men 3.7 L · women 2.7 L
Practical tips
- Keep a bottle where you work; most shortfalls are forgetfulness, not effort.
- Drink with each meal; it adds up to most of the target.
- Weigh yourself before and after a long workout: each kilogram lost is about a liter to replace.
- Log water in your food tracker if you want a daily total next to your meals.
Questions
How much water should I drink a day?
The U.S. National Academies set an adequate intake for total water of about 3.7 liters a day for men and 2.7 liters for women, from all drinks and food. Roughly 80% usually comes from drinks, so about 3.0 L and 2.2 L of fluids, plus more when you exercise or it is hot.
Does coffee or tea count toward water intake?
Yes. Caffeinated drinks still contribute to daily fluid intake for people who drink them regularly. Water-rich foods such as fruit, vegetables and soup count too.
Is the 8 glasses a day rule true?
It is a reasonable reminder rather than a scientific rule. Eight 250 ml glasses is 2 liters, slightly under the drink share of the reference values for most adults.
How do I know if I am drinking enough?
Pale yellow urine and rarely feeling thirsty are good everyday signs. Needs rise with heat, exercise, illness, pregnancy and breastfeeding.
Sources
- Institute of Medicine. Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate. National Academies Press; 2005.
- American College of Sports Medicine. Exercise and fluid replacement position stand. Med Sci Sports Exerc. 2007;39(2):377–390.
Built and checked by Ingrid Solberg. Last reviewed October 22, 2026. All formulas: formulas & sources.