Water Intake Calculator

How much water you should drink per day based on weight, activity and climate.

min
2.66Liters per day
90US fluid ounces
11.28-oz glasses
250 ml cups
10.6
500 ml bottles
5.3
Spread over 16 waking hours
166 ml per hour

About 20% of daily water typically comes from food, so you may need slightly less as drinks. Thirst and pale-yellow urine are good real-time guides.

General guidance only. Fluid needs vary and some medical conditions require specific limits. Ask a healthcare professional if unsure.

About the Water Intake Calculator

How much water should you drink a day? The often-quoted "8 glasses" is a rough average, not a rule. Real needs scale with body size, activity and environment. This calculator starts from roughly 33 ml of water per kilogram of body weight, adds about 350 ml for every 30 minutes of exercise, and adjusts for hot climates, pregnancy and breastfeeding.

The result is total water from beverages and includes ordinary drinks such as tea, coffee and milk, which do count towards hydration. Around a fifth of your daily water usually comes from food, especially fruit and vegetables.

People with heart or kidney conditions, and anyone advised to restrict fluids, should follow their doctor's guidance rather than a general calculator.

How to use the Water Intake Calculator

  1. Enter your body weight in kilograms or pounds.
  2. Add the minutes of exercise you do on a typical day and select your climate.
  3. If relevant, choose pregnancy or breastfeeding. Read your daily target in liters, ounces and glasses.

Frequently asked questions

Do coffee and tea count towards water intake?

Yes. Caffeinated drinks have a mild diuretic effect but still provide a net gain of fluid. Very high caffeine intake may reduce the benefit, and sugary drinks add calories, so plain water remains the best default.

Can you drink too much water?

Yes, though it is rare. Drinking several liters within an hour or two can dilute blood sodium (hyponatremia), which is dangerous. Spread intake across the day and let thirst guide you, especially during endurance events.

How do I know if I am dehydrated?

Common signs are thirst, dark yellow urine, headache, tiredness and dry mouth. Pale straw-coloured urine generally indicates good hydration.

Should I drink more when it is hot?

Yes. Sweating increases fluid loss, so the calculator adds about 10% for hot or humid climates. Drink before you feel thirsty on very hot days and during long outdoor activity.