Daily Water Intake
"Two litres a day" is not a number that fits everyone.
Reading your result
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How it is calculated
The two-litre rule assumes an average body. A 50kg and a 90kg person cannot need the same volume. Guidelines commonly land at 30–35ml per kilogram; this calculator uses 33.
Total need and glasses to drink are different numbers. Food supplies 20–30% of daily fluid, more on a diet heavy in soup, fruit and vegetables.
Thirst arrives late — after mild dehydration has already set in. Pale yellow urine indicates enough, dark yellow indicates a shortfall, and that check is more practical than counting.
More is not better. Drinking large volumes quickly carries a hyponatraemia risk, and kidney or heart conditions can require restriction. Follow clinical advice where it applies.
Frequently asked questions
Do coffee and tea count?
Yes. Caffeine has a mild diuretic effect but not enough to offset the fluid consumed. Alcohol is the exception and should be treated separately.
How much extra when exercising?
Replace what you sweat. Around 350ml per 30 minutes is a starting point, rising with heat and intensity. Weighing yourself before and after gives the exact loss.
Can I drink it all at once?
Spread it out. Large single volumes are substantially excreted rather than absorbed.
A general estimate that varies with climate, activity, diet and medical conditions. Follow clinical advice if fluid restriction applies to you.