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Follow channelDaily Water Intake Calculator: EFSA and NASEM Adequate Intake, Adjusted for Exercise and Heat
Get your adequate daily water intake from EFSA and the US National Academies (NASEM), then add the range you lose in sweat during exercise from the American College of Sports Medicine (ACSM).
Not medical advice. People with kidney or heart disease or on diuretics should follow their doctor.
Reference values (total water from drinks and food)
| Group | EFSA (2010) | NASEM (2004) |
|---|---|---|
| Men (14+) | 2.5 L | 3.7 L (19+) |
| Women (14+) | 2.0 L | 2.7 L (19+) |
| Pregnant | 2.0 + 0.3 L | — |
| Breastfeeding | 2.0 + 0.7 L | — |
| Boys 9–13 | 2.1 L | — |
| Girls 9–13 | 1.9 L | — |
| 4–8 years | 1.6 L | — |
| 2–3 years | 1.3 L | — |
How it works
- The base is EFSA's adequate intake for your group, including water in food. For adults we also show the higher NASEM value, so you see the range between the two.
- 80% from drinks: NASEM states about 80% of water comes from beverages and 20% from food; we apply the same split to the EFSA value as an estimate.
- Exercise: ACSM gives predicted sweat rates of 0.4 to 1.8 L per hour depending on body mass, pace and temperature. We multiply that range by your session length.
- Heat: EFSA says its values apply to moderate temperature and activity, and losses under extreme conditions can reach about 8,000 mL a day.
Sources
- EFSA NDA Panel (2010). Scientific Opinion on Dietary Reference Values for water. EFSA Journal 8(3):1459
- National Academies (IOM, 2004): Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate — 3.7 and 2.7 L; 80% from beverages
- ACSM (2007). Exercise and Fluid Replacement. Med Sci Sports Exerc 39(2):377-390 — sweat rates 0.4–1.8 L/h
Sources checked: 2026-10-25
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FAQ
Do I need 8 glasses a day?
The 8-glass rule is not in these references. EFSA sets 2.0 L for women and 2.5 L for men from all sources, food included.
Why is NASEM higher than EFSA?
Both are based on observed intakes of healthy people in different surveys (US/Canada vs Europe), so the numbers differ. We show both as a range.
How do I know my sweat loss?
Weigh yourself before and after training without wet clothes. Each kg lost is roughly a litre of water. ACSM advises keeping losses under 2% of body weight.
Do coffee and tea count?
Yes. NASEM says caffeinated drinks count toward total water.