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Water Intake Calculator

A daily water target built from your body weight, how much you train and the climate you live in, plus what the evidence actually says about hydration and fat loss.

Daily water target3.09 LAbout 12 glasses of 250 ml (8 fl oz)

Baseline2.73 L35 ml per kg

Exercise+0.36 L12 ml per minute

Climate+0 LHeat allowance

Range2.8 L – 3.4 L±10%

Around 20% of your fluid comes from food, and tea, coffee and milk all count. Pale-yellow urine and rarely feeling thirsty means you are hydrated, whatever the number says. Water also helps with appetite: a glass before meals modestly reduces intake in trials.

How the estimate works

Dietitians commonly use 30–35 ml per kilogram of body weight as a baseline for healthy adults, which lines up with the European Food Safety Authority's adequate intake of 2.0 L (women) and 2.5 L (men) for people of average size. We add about 12 ml for every minute of sweaty exercise and a 500 ml allowance for hot or humid climates. Pregnancy and breastfeeding add roughly 300–700 ml.

Hydration during a diet

Cutting calories usually means cutting food-borne water too, and lower carbohydrate intake sheds glycogen-bound water in the first week. Both raise the amount you need to drink. A simple check: pale-yellow urine and rarely feeling thirsty means you are on track, whatever the calculator says.

Frequently asked questions

Is "eight glasses a day" true?

It is a rough average, not a rule. Needs scale with body size, activity and climate, which is why a 55 kg office worker and a 95 kg builder need very different amounts. About 20% of your water also comes from food.

Does coffee dehydrate you?

No. Moderate caffeine has a negligible diuretic effect in regular drinkers, and coffee, tea and milk all count towards your total.

Can drinking water help me lose weight?

Modestly. Trials show that 500 ml of water before meals reduces intake at that meal, and thirst is often mistaken for hunger. It is a helpful habit, not a fat burner.

Can I drink too much?

Yes, though it is rare. Drinking many litres in a short time during endurance events without electrolytes can cause hyponatremia. Spread intake through the day and drink to thirst during long efforts.

Go deeper

Nutrition On a GLP-1 Medication? Protein and Muscle Matter More, Not Less How GLP-1 medications change appetite, why under-eating protein costs you muscle, practical protein, fiber, and fluid targets, and nausea-friendly foods. Nutrition How to Be Less Hungry on a Diet Why hunger rises in a calorie deficit and how to blunt it with protein, fiber, food volume, meal timing, sleep, and knowing when the deficit is simply too big. Mindset Sleep, Stress and the Scale Short sleep raises hunger hormones and shifts weight loss away from fat; stress adds water weight and drives snacking. What the evidence says and what to do.

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Ethereal provides general educational information and estimates only. It is not medical advice and does not replace an assessment by a doctor or registered dietitian. Do not use it if you are under 18, pregnant, or have a history of disordered eating without professional guidance. Read the full disclaimer.