Water Intake Calculator
Get a personal daily water target from your body weight, activity and climate, shown in ounces, litres, cups and bottles.
- Weight-based
- Exercise & climate
- oz, litres & cups
- Formula shown
Daily water intake
Fill in the boxes. The answer appears as you type.
How much water should you drink?
A common rule of thumb is to drink half your body weight in pounds as fluid ounces of water each day, plus about 12 ounces for every 30 minutes of exercise, and a little more in hot or humid weather. For a 160 lb person that is about 80 oz (2.4 litres). The US National Academies’ adequate intake for total water from all drinks and food is about 3.7 litres a day for men and 2.7 litres for women, of which roughly 80% comes from drinks. Your needs vary with health, diet and activity, so treat the result as a starting point and drink to thirst.
How to use Water Intake Calculator
- Enter your weight and choose pounds or kilograms.
- Add your daily exercise in minutes.
- Choose hot or humid if that applies.
- Read your target in litres, ounces, cups and 500 ml bottles.
Hydration guidelines
- Rule of thumb: body weight (lb) × 0.5 = ounces of water a day.
- Add about 12 oz (350 ml) for every 30 minutes of exercise.
- US adequate intake for total water: about 3.7 L/day for men, 2.7 L/day for women (food included).
- Pale yellow urine is a simple sign of good hydration.
Why use this water intake calculator
- Answers as you typeNo Calculate button. Change any number and every result updates instantly.
- Clear, sourced rules of thumbEach formula is named and explained, so you know where the number comes from and its limits.
- Every unitLitres, fluid ounces, 8 oz cups and 500 ml bottles, plus an hourly target.
- PrivateYour numbers are calculated on your device and never sent anywhere.
Common uses
- Daily hydration goal. Set a target for a water bottle or app.
- Training days. Add fluid for workouts.
- Hot weather. Adjust for heat and humidity.
- Weight loss plans. Many plans include a water target.
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Example: 160 lb with a 30-minute workout
Base 160 × 0.5 = 80 oz, plus 12 oz for exercise = 92 oz ≈ 2.7 litres ≈ 11.5 cups.
What to expect from the result
This is a general estimate for healthy adults, not medical advice. People with kidney, heart or liver conditions, and pregnant or breastfeeding people, should follow their clinician’s advice. Drinking far more than you need can be harmful.
Water Intake Calculator questions
How much water should I drink a day?
A simple estimate is half your body weight in pounds as ounces: a 160 lb person needs about 80 oz (2.4 L), more with exercise or heat.
Is 8 glasses of water a day right?
The “8 × 8” rule (64 oz) is easy to remember but not based on strong evidence. Needs vary with size, activity and climate.
Do other drinks and food count?
Yes. Tea, coffee, milk and water-rich foods all contribute. Plain water is the healthiest default.
How much water should I drink when exercising?
Roughly 12 oz (350 ml) per 30 minutes of activity, more in heat or for heavy sweaters.
Can I drink too much water?
Yes. Very large amounts in a short time can cause hyponatremia (low blood sodium). Drink steadily through the day and to thirst.