Water Intake Calculator: How Much to Drink
By Hesaplayıcı
The water intake calculator finds how much water an adult needs a day with the values of the European Food Safety Authority (EFSA). Choose woman, man, pregnant or breastfeeding. It shows the total water including food, the part to drink and how many glasses that is. The result is not medical advice.
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
How to use
- Choose For whom?: Adult woman, Adult man, Pregnant woman or Breastfeeding woman.
- Press Calculate. The result shows the total water a day, the water to drink and the number of glasses.
Formula
Total water = EFSA adequate intakeWater to drink = total water × 80%Glasses = water to drink / 0.2 L
Total water is the daily water from drinks and from food. EFSA’s adequate intakes are 2.0 L for women and 2.5 L for men, plus 0.3 L in pregnancy and about 0.7 L when breastfeeding. Adult values apply from 14 years. Like the British Dietetic Association (BDA), the calculator assumes 80% of the water comes from drinks. A glass is 200 ml.
Worked example
The worked example on this page shows an adult woman. The steps give EFSA’s total water value, the part to drink and the number of 200 ml glasses.
Limits
The values are for a moderate climate and moderate activity. Water lost in hot weather and exercise must be replaced on top; EFSA gives no fixed amount for it, so the calculator adds none. Rules in ml per kg of body weight can give other results; the calculator follows EFSA. Children have other values. With kidney, heart and some other diseases your doctor sets the fluid amount.
Frequently Asked Questions
How many litres of water should I drink a day?
EFSA sets the total water need of an adult woman at 2.0 L a day and of a man at 2.5 L. Most of it comes from drinks; the BDA advises about 1.6 L of drinks for women and 2.0 L for men.
How many glasses of water a day?
With 200 ml glasses, about 8 for women and about 10 for men (BDA). Drinks other than water count too.
Do I need more water in pregnancy or when breastfeeding?
Yes. EFSA advises 300 ml more a day in pregnancy and about 700 ml more when breastfeeding.
How much more should I drink when I exercise?
The EFSA values are for a moderate climate and moderate activity; water lost through sweat must be replaced on top. The amount depends on the person, the weather and the exercise, so the calculator adds none.
Calculation rules
- The values are EFSA’s adequate intakes (EFSA Journal 2010;8(3):1459): 2.0 L of total water a day for women, 2.5 L for men; 300 ml more in pregnancy and about 700 ml more when breastfeeding. Adult values apply from 14 years.
- Total water is the water from drinks and from food. Like the British Dietetic Association (BDA), the calculator assumes 80% comes from drinks; a glass is 200 ml.
- The values are for a moderate climate and moderate activity. Water lost in hot weather or exercise must be replaced on top; EFSA gives no fixed amount for it, so the calculator adds none.
- Rules in ml per kg of body weight can give other results; the calculator follows EFSA.
- With kidney, heart and some other diseases a doctor sets the fluid amount. The result is not medical advice.