By Coach Jeff Alagar, NASM Physique and Bodybuilding Coach and ISSA Certified Nutritionist. Updated November 2026.
A good baseline is about 35 ml of water per kg of body weight a day, plus about 500 ml for every 30 minutes of exercise and another 500 ml in hot, humid weather.
How this water intake calculator works
The base is 35 ml/kg. Exercise adds 500 ml per 30 minutes, and hot climates add 500 ml for extra sweat. About a fifth of daily water comes from food such as rice, fruit and soup, so the number is a ceiling for drinks, not a strict quota.
Frequently asked questions
Do coffee and tea count?
Yes. Moderate coffee and tea still hydrate overall. Alcohol does not.
Do I need electrolytes?
For runs or sessions over an hour in the heat, yes. Add sodium, not just water, to avoid cramps and low sodium.
Related calculators
These calculators give general estimates for healthy adults and are not medical advice. If you are pregnant, under 18, or have a medical condition, ask your doctor before changing your diet or training.
