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How much water should you drink a day?
Quick answer
A simple estimate is about half a fluid ounce of water per pound of body weight a day (30 to 36 ml per kg), adjusted for heat, exercise and your doctor's advice. With a smaller appetite, it's easy to drink less without noticing.
About 88 fl oz of water a day, or roughly 11 glasses of 8 fl oz.
How we calculate it
- About 32 ml per kg for women, 36 ml per kg for men and 34 ml per kg if you'd rather not say (roughly 0.49, 0.55 and 0.52 fl oz per lb).
- The result is kept between 61 and 118 fl oz a day (1.8 to 3.5 liters).
Limits
- Kidney or heart problems, or a fluid limit from your doctor, change the math: follow your doctor.
- Food has water too, so the number is a reference, not a rule.
Sources
- Dietary Reference Intakes for water (National Academies of Sciences, Engineering, and Medicine, 2005).
- EFSA dietary reference values for water (2010).
Reviewed on November 7, 2026. General information, pending review by a health professional. Leve doesn't replace your doctor's advice.
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