Water intake calculator

How this is calculated

This calculator starts from a base of 35 ml of water per kilogram of body weight — a commonly used baseline for healthy adults — then adds extra water for exercise and hot climates, since both increase fluid loss through sweat.

• Base need = weight (kg) × 35 ml
• Exercise adds roughly 350–1400 ml depending on how intense and frequent your activity is.
• Hot or humid climates add another 350–600 ml to account for extra sweating.

Does this include water from food and drinks?

The result reflects total fluid needs, which can come from plain water, other beverages, and water-rich foods like fruits, vegetables, and soups — not only from glasses of plain water. Coffee and tea count too, in moderation, though very high caffeine or alcohol intake can increase fluid loss.

Signs you may need more water

• Dark yellow urine (pale straw color is the target)
• Feeling thirsty, tired, or getting headaches more than usual
• Dry mouth or noticeably reduced urination

These estimates are general guidance, not medical advice. People with kidney, heart, or other conditions that affect fluid balance should follow guidance from their doctor instead of a general calculator like this one.