Calories & Nutrition tool
Water Intake Calculator
Find how much water you need a day from food and drinks, using the adequate intakes, with extra for exercise, hot weather, pregnancy and breastfeeding. Free.
Nothing you enter leaves your device.
Inputs
Results
Enter values to see your results.
Simple steps
How it works
- 01
Choose your sex and, if it applies, pregnancy or breastfeeding.
- 02
Enter your exercise a day and the weather.
- 03
Select Calculate to see your total water and how much to drink.
Good to know
Frequently asked questions
How much water do adults need?
The adequate intakes set by the US National Academies are about 3.7 litres a day for men and 2.7 litres for women, from all food and drinks.
Why is the drinking amount lower than the total?
Food gives about a fifth of the water you take in. The calculator shows both the total and the part to drink.
How much extra do I need for exercise?
Sweat losses vary from about 0.4 to 0.8 litres an hour. The calculator adds 0.6 litres for each hour of exercise.
Do tea and coffee count?
Yes. All drinks count towards your water, including tea, coffee and milk. Water is the best everyday choice.
Can I drink too much?
Yes. Drinking far more than you need in a short time can be dangerous. If you have kidney or heart problems, follow your doctor's advice on fluids.
Is anything I enter stored or sent?
No. The calculation runs in your browser. Nothing you type is saved or sent to a server.
How it is calculated
Adequate total water from the Institute of Medicine (2005): 3.7 L a day for men, 2.7 L for women, 3.0 L in pregnancy and 3.8 L when breastfeeding; about 80% comes from drinks. Exercise adds 0.6 L an hour (ACSM range 0.4–0.8 L) and hot weather 0.5 L.
Sources
- Institute of Medicine. Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate. National Academies Press, 2005
- American College of Sports Medicine. Exercise and fluid replacement (position stand). Med Sci Sports Exerc 2007;39:377–90
Last reviewed: October 14, 2026