Water Intake Calculator
Free water intake calculator: how much water to drink a day for your weight and exercise, in litres or ounces and cups, with official reference values.
What it does
How much water you need depends on your body size, how much you move and the climate. This calculator uses a common rule of 35 mL per kilogram of body weight, adds about 0.6 L for each hour of exercise and the extra recommended in pregnancy and breastfeeding, and shows the result in litres (or ounces) and cups. It also shows the official reference values for total water, which include the water in food.
How to use it
- Choose your units and sex and type your weight.
- Type how many minutes you exercise on a typical day.
- If it applies, choose pregnancy or breastfeeding to add the extra water.
These are estimates for healthy adults and do not replace advice from a doctor, dietitian or coach. The calculation runs in your browser.
Frequently asked questions
Do coffee, tea and food count?
Yes. All drinks count, including coffee and tea in normal amounts, and food usually provides about a fifth of the water you take in, more if you eat a lot of fruit and vegetables.
How do I know I am drinking enough?
Pale yellow urine and not feeling thirsty are good signs. Dark urine, headache and tiredness can mean you need more, especially in hot weather or after exercise.
Can I drink too much water?
Yes, although it is rare: drinking several litres in a short time, as in long endurance events, can dilute the sodium in the blood (hyponatremia). Spread your drinking through the day.
Why are the official values different?
The US National Academies set 3.7 L a day for men and 2.7 L for women, and the European Food Safety Authority 2.5 L and 2.0 L. Both count water from drinks and food; they are averages for healthy adults, not strict targets.
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National Academies — Dietary Reference Intakes for Water (2004)
EFSA — Dietary reference values for water (2010)