Water Intake Calculator
Estimate daily fluid needs based on body weight, activity, climate, and exercise duration.
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Adjustments
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Daily fluid target
115 oz
About 14.4 cups, or 3.4 litres
Includes your inputs, the full breakdown, and every row of the table.
From drinks
92 oz
Roughly 80% of intake
From food
23 oz
Fruit, vegetables, soups
Exercise addition
18 oz
For 45 min of activity
Standard bottles
4.8 × 24 oz
What this means
- Thirst is a reliable guide for most healthy adults. Urine that is pale yellow rather than dark is the simplest practical check.
- Drinking far beyond need is not harmless — hyponatremia from excessive plain water during endurance events is a real and occasionally fatal risk. Replace electrolytes during long or hot sessions.
How the water intake calculation works
The familiar 'eight glasses a day' has no scientific origin. Actual fluid needs scale with body size, activity, environment, and diet. A common starting point is 30-35 mL per kilogram of body weight, adjusted upward for exercise and heat.
About 20% of total water intake comes from food in a typical diet, and all beverages count toward the total — including coffee and tea. The mild diuretic effect of caffeine does not offset the fluid the drink itself provides.
Frequently asked questions
Does coffee dehydrate you?
No. At habitual intakes the diuretic effect is modest and the fluid in the drink more than compensates. Caffeinated beverages count toward daily fluid intake.
How much water during exercise?
Roughly 350-500 mL per 30 minutes of moderate activity, more in heat. For sessions over an hour, or in high heat, include sodium and other electrolytes.
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Disclaimer. This calculator is provided for general information and educational purposes only and does not constitute financial, tax, legal, medical, or engineering advice. Results are estimates based on the inputs you provide and the assumptions described above. Confirm any figure with a qualified professional before acting on it.