EFSA (Europe)
2.5 L per day
European Food Safety Authority, 2010
Total water including food — about 0.5 L of this typically comes from food.
Daily Water Intake On-device
Published reference values for daily water intake — computed entirely on your device.
Sex
Weight
IOM (U.S.)
3.7 L per day
U.S. National Academies (IOM), 2004
Total water including food — about 0.7 L of this typically comes from food.
Rule of thumb
Enter your weight to see this figure.
33 ml per kg of body weight — a common rule of thumb, not an official recommendation.
Exercise, hot weather, fever, and pregnancy or breastfeeding all increase water needs — treat these figures as baselines for temperate conditions.
Why not "8 glasses a day"?
Eight 8-oz glasses come to about 1.9 L — below the reference values above. The figure traces to a 1945 note read out of context, which already counted water from food (Valtin, 2002).
Reference values for healthy adults — not medical advice. Water needs vary with activity, climate, pregnancy, and health conditions; consult a clinician if you are unsure.
Free daily water intake calculator with EFSA and IOM reference values, a weight-based rule of thumb, and the story behind the "8 glasses a day" myth. Works entirely on your device.
About this tool
What you provide
- Your sex
- Your weight, needed only for the rule-of-thumb figure
What you get
- EFSA (2010) and IOM (2004) reference values in litres per day, with the share that typically comes from food
- A weight-based rule-of-thumb figure of 33 ml per kg
Limits
- Reference values for healthy adults — not medical advice; consult a clinician if you are unsure.
- The 33 ml per kg figure is a common rule of thumb, not an official recommendation.
- These are baselines for temperate conditions; exercise, hot weather, fever, pregnancy and breastfeeding all increase water needs.
How to use it
-
Choose male or female
Press Male or Female; the EFSA and IOM reference figures are published separately for each.
-
Enter your weight
Switch the weight unit to kg or lb and type your weight — it is used only by the rule-of-thumb card.
-
Compare the three figures
Read the EFSA, IOM and rule-of-thumb cards side by side; each gives litres per day and notes roughly how much of that typically comes from food, and the section below explains where the eight-glasses figure came from.
Frequently asked questions
How much water should I drink per day?
The tool gives you published reference values for daily water intake based on your inputs, computed entirely on your device.
Is this medical advice?
No, it reports reference figures only; for your personal hydration needs, consult a clinician.
Is it free and does it need an account?
Yes, it's free with no signup, and nothing is uploaded since the calculation runs entirely on your device.