According to the European Food Safety Authority (EFSA), an adequate water intake is about 2.0 litres a day for adult women and 2.5 litres for adult men — but that is total water, from drinks and food together. It is a starting point, not a rule: your needs depend on activity, weather, health and diet.
Total water versus water from drinks
The recommendations refer to total water: water you drink, tea, coffee, milk and soup, plus the moisture in fruit and vegetables. Roughly a fifth of the day’s water usually comes from food and the rest from drinks. So “2 litres” does not mean 2 litres of plain bottled water.
EFSA states its values as an “adequate intake” — a level assumed to be enough for healthy people, not an individual requirement you must hit to the millilitre.
What official guidance says
EFSA considers about 2.0 L of water a day adequate for adult women and about 2.5 L for adult men, in moderate temperatures and with moderate activity. For children it gives lower, age-specific values.
The US National Academies of Sciences, Engineering, and Medicine (NASEM) give higher figures: about 2.7 L for women and 3.7 L for men, also as total water from drinks and food. The difference reflects different methods and populations — neither number is “wrong”.
Why a single universal target is not enough
Your needs change from day to day. The most common factors:
- hot or humid weather — you lose more water in sweat,
- exercise (see How Much Water Should You Drink During Exercise?),
- pregnancy and breastfeeding — EFSA suggests roughly 0.3 L extra in pregnancy and 0.7 L extra while breastfeeding,
- fever, vomiting or diarrhoea,
- age — older adults may feel thirst less strongly,
- diet — plenty of fruit and vegetables supplies more water, while a very salty diet raises the need to drink,
- high altitude and some medicines (for example diuretics).
How to tell if you are drinking enough
For most healthy adults, thirst and urine colour work well: pale yellow usually means good hydration, dark yellow suggests you should drink. These are only rough guides — urine colour is also changed by vitamins, medicines and some foods. We describe the symptoms of low fluid levels in Signs of Dehydration.
Important: if you have heart, kidney or liver disease, or a doctor has told you to limit fluids, set your goal with your doctor. Very large amounts of water in a short time can also dilute sodium in the blood (hyponatraemia) — rare, but dangerous.
How to set your goal and stick to it
Start with the EFSA figure, subtract about 20% for water from food, and adapt to your day — we walk through it in How to Estimate Your Daily Water Needs.
In the WODA app you set your own daily goal, log the water you drink quickly and see your progress. It is a habit tool, not a medical device. For ideas on staying consistent, see How to Remember to Drink Water.
Frequently asked questions
Is the “8 glasses a day” rule true?
It is a convenient rule of thumb, not the result of research into individual needs. The NHS suggests roughly 6–8 glasses of fluid a day as a guide, but the right amount depends on the person and conditions.
Do coffee and tea count towards my daily fluids?
Yes, in moderate amounts. See Do Coffee and Tea Count Toward Daily Hydration?.
Can you drink too much water?
Yes, although it is rare: very large amounts in a short time can lower blood sodium. Drink steadily through the day and do not force yourself to drink beyond thirst unless a doctor advises it.
Do I need to drink if I am not thirsty?
Most healthy adults regulate well by thirst. Reminders help when you forget during a busy day; older adults may feel thirst less, so regular drinking matters more for them.
Sources
- EFSA — Scientific Opinion on Dietary Reference Values for water (EFSA Journal 2010;8(3):1459)
- National Academies — Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate (2005)
- NHS — Water, drinks and hydration
This article is for information only and does not replace advice from a doctor or dietitian. If you are unsure or have worrying symptoms, contact a doctor.