Water Intake Calculator
HealthFind out how much water you should drink each day, based on your weight and how active you are.
Your kidneys can process about 0.8–1 litre per hour — spread your intake through the day rather than drinking large amounts at once.
What is this water intake calculator based on?
It scales a clinically-cited adequate-intake range — roughly 30 ml/kg of body weight for a sedentary person up to 40 ml/kg for someone very active — by your own weight and activity level. More activity means more fluid loss through sweat, so the per-kg rate rises with it.
Worked Example — 70 kg, Moderate activity
Frequently Asked Questions
Common Mistakes to Avoid
- This is weight and activity only — not age, sex, or climate. Hot weather, illness, and individual differences all change real needs; treat the result as a starting baseline, not an exact prescription.
- Pregnancy, breastfeeding, and creatine use aren't factored in. All three genuinely increase water needs beyond this formula — use this as a baseline and add to it based on your doctor's or a nutrition guide's specific advice.
- More water isn't unlimited water. Drinking far beyond your calculated need doesn't add benefit and, in extreme excess, can be harmful — this number is a target, not a floor to exceed.
References
- European Food Safety Authority (EFSA)
- American College of Sports Medicine (ACSM)
Last reviewed July 2026
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