Water Intake Calculator: How Much Water Should I Drink a Day?

How much water should I drink a day?

This calculator starts from 32 ml of fluid per kg of body weight (about 0.5 oz per lb), then adds 12 ml for every minute of exercise (roughly 0.7 L an hour), extra for hot or humid weather (350–1,100 ml) and, if you are female, for pregnancy (+300 ml) or breastfeeding (+700 ml). The range shown is the target ±15%, because needs genuinely vary between people and days.

For comparison, the U.S. National Academies set adequate total water intake at about 3.7 L a day for men and 2.7 L for women, roughly 80% of it from drinks and 20% from food. Tea, coffee, milk, juice and the water in fruit, vegetables and soup all count.

Signs you are drinking enough

• Pale yellow urine (dark yellow means drink more; completely clear all day can mean you are overdoing it).
• You rarely feel thirsty, and your mouth and lips are not dry.
• Steady energy and no dehydration headaches.

Can you drink too much water?

Yes, but it is rare. Drinking several litres in a short time can dilute blood sodium (hyponatremia), which is dangerous. Spread your intake through the day, and do not force fluids well beyond thirst. People with kidney, heart or liver disease, or on diuretics, should follow their doctor's advice on fluid limits.

Questions

Does coffee or tea count?

Yes. Caffeinated drinks hydrate you overall for regular drinkers, though water is the best default.

Do I need 8 glasses a day?

“8 glasses” (about 1.9 L) is a handy rule of thumb, not a requirement. Your result depends on your size, activity and climate.

Is my data private?

Yes. Your numbers and tracker stay in this browser.

General information, not medical advice. Related: Macro Calculator · BMR Calculator · BMI Calculator