Weight-based formula
Activity & climate adjusted
Litres + glasses shown
Hydration Science

How much water
should you
drink today?

Your daily water needs depend on your weight, how active you are, and where you live. Get your personalised target in litres and glasses.

Weight-based Activity adjusted Climate factor
2.5L 2.0L 1.5L — L per day 🥛 🥛 🥛 🥛 🥛 🥛 ~8 glasses · 250ml each
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Water Intake Calculator

Your personalised daily hydration target

Your daily water target
—
litres per day

Visualised as glasses (250 ml each)

Based on the 35 ml/kg baseline formula adjusted for activity and climate. Individual needs vary with health status, diet, and medications. These figures include water from all fluids and food. About 20% of daily water intake typically comes from food.

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Hydration tip

Drink a large glass of water first thing in the morning before coffee. Your body loses about 500 ml overnight through breathing and sweating — rehydrating early improves energy and focus for the rest of the day.

How much water do you actually need?

The amount of water your body needs each day varies significantly based on your size, how active you are, the temperature of your environment, and your overall health. The widely cited "8 glasses a day" guideline is a rough average — not a personalised recommendation.

The most evidence-based approach uses body weight as the primary baseline: approximately 35 ml per kilogram of bodyweight per day for a moderately active adult in a temperate climate. This produces a starting estimate that is then adjusted upward for higher activity levels and hotter climates, both of which substantially increase fluid losses through sweat.

Factors that increase your needs

Exercise significantly increases water requirements — even moderate exercise can increase losses by 500–1,000 ml per hour depending on intensity and temperature. Hot and humid climates increase baseline needs. Pregnancy adds approximately 300 ml per day, and breastfeeding adds 700–1,000 ml. High-fibre diets, high protein intake, certain medications, and illness also raise requirements.

Water needs by activity level

ActivityExtra water needed
SedentaryBaseline only
Light exercise (1–3x/week)+300–500 ml/day
Moderate exercise (3–5x/week)+500–700 ml/day
Hard daily exercise+700–1,000 ml/day
Intense athletic training+1,000+ ml/day

Signs of dehydration

The most reliable indicator of hydration status is urine colour. Pale straw yellow is ideal. Dark yellow or amber signals dehydration. Other signs include fatigue, reduced concentration, headaches, dry mouth, and dizziness. Thirst is a useful but delayed signal — mild dehydration has already occurred by the time thirst appears.

Frequently asked questions

General guidelines suggest around 35 ml per kilogram of bodyweight per day as a baseline. A 70 kg person needs roughly 2.45 litres daily. Needs increase significantly with exercise, hot climates, pregnancy, and breastfeeding. The "8 glasses a day" rule is a rough guide — personalised calculation is more accurate.
Yes. Despite the mild diuretic effect of caffeine, research shows caffeinated beverages like coffee and tea still contribute to net fluid intake. The water in these drinks outweighs any fluid loss from the diuretic effect. However, plain water remains the best primary hydration source.
The simplest indicator is urine colour. Pale straw yellow indicates good hydration. Dark yellow or amber suggests you need more fluids. Other signs of dehydration include fatigue, headaches, dry mouth, and difficulty concentrating. Thirst is reliable but typically appears only after mild dehydration has already begun.
Yes, though it is rare in healthy adults. Drinking excessive amounts in a short time can cause hyponatremia — dangerously low blood sodium. This is most common in endurance athletes who drink large volumes of plain water without electrolytes. For most people, following thirst cues and hitting the recommended daily target is safe.
Adequate hydration can support weight loss indirectly. Drinking water before meals reduces appetite and calorie intake in some studies. Staying well-hydrated also supports optimal metabolism and exercise performance. Some research suggests drinking 500 ml of water temporarily increases metabolic rate by 24–30% for about an hour.