How much water to drink a day: water calculator
“8 glasses a day” isn’t a universal rule —
your needs depend on your sex, age, weight,
activity and the weather.
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Calculate your daily water target
Two numbers: all the fluid you need in a day, and how much of it should be plain water
Kids need different amounts — see Who needs to drink more water
Counted as fluid (7 fl oz a cup)
A 5-oz glass of wine, 12-oz beer or 1.5-oz shot — +1.7 fl oz of water
How we calculated this
- Base need — weight, sex, age84 fl oz
- Total fluids a day84 fl oz
- Water from food — vegetables, fruit, soups (20%)−16 fl oz
- Plain water left68 fl oz
With heart failure, kidney disease or cirrhosis, daily fluids are usually limited to 34–51 fl oz (1.0–1.5 L) — and your doctor should set the exact number, because it depends on swelling, blood sodium and your medications.
Don’t go by general guidelines — they’re for healthy kidneys and a healthy heart.
This is a guide, not medical advice. If you have kidney or heart disease, your doctor sets your number.
Know your number — now make every glass filtered and hydrogen-rich
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