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.
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 the calculation adds nothing fixed for it. 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