Water Intake Calculator
Find out how much water you need daily based on your weight, activity level, and climate. Get personalized hydration recommendations in ounces and milliliters.
💡 Tip: Drink water throughout the day, not all at once. Increase intake during exercise, illness, or pregnancy.
How Much Water Do You Really Need?
The old "8 glasses a day" rule is a decent starting point, but your actual water needs depend on several factors: body size, activity level, climate, diet, and health status. This calculator uses evidence-based formulas to give you a personalized recommendation.
The Formula
Base intake = Body weight × 0.5 oz per pound (or 30 ml per kg)
This gives you your baseline hydration need. Then we adjust for:
- Activity: Multiply by 1.0-1.8 based on exercise frequency. Each 30 minutes of exercise adds ~12 oz (350 ml).
- Climate: Multiply by 1.0-1.3 based on temperature. Hot weather increases sweat loss significantly.
Signs You're Hydrated
- Urine is pale yellow (like lemonade, not apple juice)
- You're not thirsty
- Your mouth feels moist
- You have steady energy throughout the day
Signs You Need More Water
- Dark yellow urine
- Headaches or fatigue
- Dry mouth or skin
- Dizziness when standing
- Constipation
Can You Drink Too Much?
Yes. Hyponatremia (water intoxication) occurs when you drink so much water that sodium levels drop dangerously low. This is rare but can happen during endurance events. Listen to your body — drink when thirsty, don't force excessive amounts.
What About Coffee and Tea?
Caffeinated beverages do count toward hydration, though they have a mild diuretic effect. For every cup of coffee, add an extra 4 oz of water to compensate. Herbal teas and decaf count fully.
Foods That Count
About 20% of daily water comes from food. High-water foods include:
- Cucumber (96% water)
- Watermelon (92%)
- Strawberries (91%)
- Lettuce (96%)
- Tomatoes (94%)