How Much Water Should You Drink a Day?
Hesaplayıcı2 min read
Short answer
The European Food Safety Authority (EFSA) sets the total water need of an adult woman at 2.0 litres a day and of a man at 2.5 litres. About 80% comes from drinks. So a woman should drink 1.6 litres, or eight 200 ml glasses, and a man 2 litres, or ten glasses. This is general information, not medical advice.
Open the calculator →Formula
total water = EFSA adequate intake
water to drink = total water × 80%
glasses = water to drink / 0.2 L
- total water: the daily water from drinks and from food. EFSA’s adequate intakes are 2.0 L for women and 2.5 L for men; adult values apply from 14 years.
- pregnancy and breastfeeding: EFSA adds 0.3 L in pregnancy and about 0.7 L when breastfeeding. The pregnancy increase follows the increase in energy intake.
- 80%: the British Dietetic Association (BDA) says 70–80% of the water comes from drinks and the rest from food. The calculation uses 80%.
- 0.2 L: one glass, 200 ml
Step-by-step example
An adult woman:
- Total water: the EFSA value, 2 L.
- Water to drink: 2 × 80% = 1.6 L.
- Glasses: 1.6 / 0.2 = 8 glasses.
Drinks other than water count towards this amount.
How much water for whom?
| For whom? | Total water | From drinks | 200 ml glasses |
|---|---|---|---|
| Adult woman | 2 L | 1.6 L | 8 |
| Adult man | 2.5 L | 2 L | 10 |
| Pregnant woman | 2.3 L | 1.84 L | 9.2 |
| Breastfeeding woman | 2.7 L | 2.16 L | 10.8 |
When you need more water
The EFSA values are for a moderate climate and moderate activity. In extreme heat and hard exercise, water losses can reach about 8 litres a day, and they must be replaced on top. The amount depends on the person, the weather and the exercise, so EFSA gives no fixed amount; the water intake calculator adds 10 ml for each minute of exercise (0.6 L an hour, the middle of the 0.4–0.8 L an hour that ACSM gives as a start). Rules in ml per kg of body weight can give other results. Drinking more water, faster, than the kidneys can pass is dangerous too; EFSA puts that limit at 0.7–1.0 L an hour. With kidney, heart and some other diseases, your doctor sets the fluid amount.
Worked example: An adult woman
Water to drink
1.6 L
- Total water a day (drinks and food)
- 2 L
- Glasses (200 ml)
- 8 glasses
Step by step
Total water a day (drinks and food)
total water = EFSA (woman)
total water = 2 L = 2 L
Water to drink
from drinks = total water × 80%
from drinks = 2 × 80% = 1.6 L
Glasses (200 ml)
glasses = from drinks / 0.2 L
glasses = 1.6 / 0.2 = 8