Water Intake Calculator
Enter your weight, activity level, and climate to see your personalized daily water intake recommendation in ounces, cups, and liters.
The old "8 glasses a day" rule is a simplification — actual water needs vary by body weight, activity, and environment. The Institute of Medicine recommends roughly 0.5 oz per pound of body weight as a baseline, with increases for exercise and heat. This calculator applies those adjustments and shows your daily target in ounces, cups, and liters.
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Last reviewed: April 2026Report an error
Daily Water Intake
104 oz / 3.1 L
You should drink approximately 104 oz (3.1 liters / 13 glasses) of water per day based on your weight, activity, and climate.
Ounces
104 oz
Cups (8 oz)
13 cups
Glasses
13 glasses
Liters
3.1 L
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How to Use This Water Intake Calculator
- Enter your body weight in lbs or kg.
- Select your typical activity level.
- Select your climate (hot climates increase sweat loss).
- Read your daily water target.
- Note: this is total fluid — about 20% of hydration typically comes from food.
Frequently Asked Questions
- The Institute of Medicine recommends about 3.7 liters (125 oz) for men and 2.7 liters (91 oz) for women as total daily water from all sources. Active individuals and those in hot climates need more.
- Water is optimal. Coffee and tea count toward hydration (the diuretic effect of caffeine is mild and doesn't offset the fluid). Alcohol is dehydrating and shouldn't count toward your target.
- Dark yellow urine, thirst, headache, fatigue, and reduced performance are early signs. Pale yellow urine generally indicates good hydration. Thirst itself is a late signal — don't rely on it alone.
- Yes — hyponatremia (dangerously low blood sodium) can occur from extreme over-hydration, most commonly in endurance athletes. For typical people, the kidneys handle excess fluid safely. Stick to your calculated range and drink to thirst.
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