How Much Water to Drink a Day Calculator
This free water intake calculator estimates how much water you should drink each day based on your body weight, activity level, and climate. Staying properly hydrated supports energy, digestion, focus, and overall health, but the right amount varies from person to person. Enter your details and the calculator gives a personalized daily water goal in liters or ounces.
How to Use the Water Calculator
- Enter your weight.
- Select your activity level.
- Account for climate (hot weather increases needs).
- Calculate — see your daily water target.
How Water Needs Are Estimated
A common guideline is about 30–35 ml of water per kilogram of body weight per day, adjusted up for exercise and hot weather. For example, a 70 kg person needs roughly 2.1–2.45 liters per day at baseline, plus extra to replace fluid lost through sweat during activity.
Daily Water by Weight (baseline)
| Weight | Approx Daily Water |
|---|---|
| 50 kg | ~1.5–1.75 L |
| 70 kg | ~2.1–2.45 L |
| 90 kg | ~2.7–3.15 L |
What Increases Your Water Needs
- Exercise: add water to replace fluid lost as sweat.
- Hot or humid climate: raises fluid loss.
- Pregnancy or breastfeeding: increases requirements.
- Illness: fever, vomiting, or diarrhea raise needs.
Note: Other drinks and water-rich foods also count toward hydration. This is a general estimate, not medical advice — listen to your thirst and consult a professional for specific needs.
Frequently Asked Questions
How much water should I drink a day?
A common guideline is about 30–35 ml per kilogram of body weight, so a 70 kg person needs roughly 2.1–2.45 liters, plus more for exercise and hot weather.
Is 8 glasses a day enough?
The "8 glasses" rule (about 2 liters) is a rough average. Your actual needs depend on your weight, activity, and climate, which this calculator personalizes.
Does coffee or tea count toward hydration?
Yes — most beverages and water-rich foods contribute to your daily fluid intake, though plain water is the best primary source.
How much more water do I need when exercising?
Add fluid to replace what you lose as sweat — often an extra 0.5–1 liter per hour of intense exercise, more in heat.
Is this water intake calculator free?
Yes — it is completely free, requires no signup, and gives a personalized daily water goal.