Daily water in litres and glasses from the EFSA or US reference, plus exercise and heat
Runs in your browser. Nothing you type is sent anywhere. Checked against sources on 23 Oct 2026.Water Intake Calculator starts from a published reference. EFSA sets adequate total water at 2.0 litres a day for women and 2.5 for men, about 80% of it from drinks. A man at rest therefore drinks about 2.0 litres, eight 250 mL glasses, plus his own allowance for exercise and heat.
Choose "kg and litres" or "lb and fl oz" under Units, and pick your Sex; for Female, set Pregnancy if it applies.
Under Reference choose EFSA, "US National Academies" or "Per kg"; with "Per kg" enter your Weight and the Rate in mL/kg.
Under "Your own estimates" enter "Exercise a day", "Sweat an hour" and any "Hot weather, extra a day".
Pick a "Glass size", read "To drink a day" and Glasses, then press "Share result".
Nobody has measured a correct amount of water for one person. What exists are reference values set by expert bodies from what healthy, adequately hydrated people actually take in. This page lets you choose one and names its source.
The European Food Safety Authority sets an adequate intake of total water of 2.0 litres a day for adult women and 2.5 litres for men, for moderate temperatures and moderate activity. It adds 300 mL a day in pregnancy and about 700 mL while breastfeeding. The US National Academies found that adequately hydrated women take in about 2.7 litres a day and men about 3.7. A third option multiplies your weight by a rate you choose; the default of 30 mL per kilogram is the top of the 25 to 30 mL range that NICE uses for routine fluid prescribing in hospital, which is a clinical figure rather than a drinking target.
All three are total water, including the moisture in food. The National Academies put the share from drinks at about 80 percent, so the page takes a fifth off for food before turning the rest into glasses of the size you choose, or US fluid ounces.
Exercise and heat have no official per-hour figure, because sweat rates vary too widely between people. The American College of Sports Medicine advises weighing yourself before and after exercise to find your own. So both allowances are your inputs, labelled as estimates, and are added straight to the drinking figure as sweat to replace. The National Academies note that very active people in constant hot weather can need six litres or more.
What the tool does not do: it cannot tell you are dehydrated, and it is not for anyone told by a doctor to limit fluids, such as people with heart or kidney failure. This is general information, not medical advice.
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EFSA sets adequate total water at 2.0 litres a day for women and 2.5 for men, and about 20% of that normally comes from food. At rest in a moderate climate, that means drinking roughly 1.6 litres for a woman and 2.0 litres for a man, or about seven and eight 250 mL glasses.
Both bodies set their values from what healthy populations were observed to consume, using different survey data and methods. The US National Academies report about 2.7 litres a day for women and 3.7 for men, against EFSA's 2.0 and 2.5. Neither is a minimum, and both include the water in food.
Yes. Every reference on this page is total water, covering tap and bottled water, tea, coffee, milk, juice and the moisture in food. The National Academies estimate about 80% comes from drinks, so the page removes a fifth for food before counting glasses. Soups, fruit and vegetables all contribute.
No single figure fits everyone, because sweat rates vary widely. The American College of Sports Medicine suggests weighing yourself before and after a typical session: each kilogram lost is about a litre of fluid. Enter that as litres per hour, and the page adds it to your daily drinking figure.
EFSA advises an extra 300 mL a day in pregnancy and about 700 mL a day while breastfeeding, on top of the 2.0 litres for women. The page adds these amounts when either option is chosen. A midwife or doctor may give different advice for a particular pregnancy.
Yes. Drinking far more than the body can excrete dilutes blood sodium, a condition called hyponatraemia, which can be dangerous, particularly during long endurance events. Anyone told to restrict fluids for heart or kidney disease should follow that advice rather than any figure here.
Rates and rules change; check the source before you rely on a figure.
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Also works as: How Much Water Should I Drink.
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