Find out how much water you need daily based on your weight, activity, and climate — personalised to your lifestyle.
Water needs vary based on individual health, medications, and conditions. People with kidney or heart conditions should consult their doctor about fluid intake.
Water is essential for virtually every bodily function: regulating body temperature, transporting nutrients, cushioning joints, flushing waste through the kidneys, and maintaining blood volume. Even mild dehydration (1–2% body weight loss through fluid) can impair cognitive function, mood, and physical performance.
Chronic inadequate hydration is linked to kidney stones, urinary tract infections, constipation, and may contribute to longer-term cardiovascular strain. Yet many people consistently under-hydrate without realising it.
The base formula uses 33 ml per kilogram of body weight as a starting point. This is then adjusted by activity and climate multipliers:
| Factor | Level | Multiplier |
|---|---|---|
| Activity | Sedentary | ×1.0 |
| Activity | Moderate | ×1.2 |
| Activity | Active | ×1.4 |
| Climate | Cold | ×0.95 |
| Climate | Temperate | ×1.0 |
| Climate | Hot | ×1.2 |
For example, a 75 kg person who is moderately active in a hot climate: 75 × 0.033 × 1.2 × 1.2 = 3.56 litres per day.
Carry a reusable water bottle and sip throughout the day rather than trying to drink large amounts at once. Eat water-rich foods like cucumbers, watermelon, oranges, and soups. Pay attention to urine colour — pale straw is well-hydrated, dark yellow suggests you need more fluid. Drink extra before, during, and after exercise.
Water needs are highly individual. This calculator provides a general estimate. People with kidney disease, heart failure, or those taking diuretics or other medications may need significantly different fluid targets. Pregnant and breastfeeding women also have increased hydration needs. Always follow your healthcare provider's guidance if you have a medical condition affecting fluid balance.
Approximately 33 ml per kg of body weight as a baseline. For a 75 kg person, that is about 2.5 litres, increasing with exercise and hot weather.
Yes — despite mild diuretic effects, coffee and tea contribute to overall hydration. Plain water and herbal teas remain the optimal choices.
Yes. Overhydration (hyponatraemia) is rare but can occur in endurance athletes or people who drink excessive amounts rapidly. Drink to thirst rather than forcing intake.