About 60% of your body is water, which is involved in temperature control, transporting nutrients and removing waste. People who train lose more through sweat, so proper hydration is a foundation for performance and health. This tool estimates the water you need per day from your weight and activity level.
How to use this tool
Enter your body weight and activity level. A common guideline is about 35 ml per kg of body weight, rising further on heavy-training days or in hot conditions. The figure shown is a total that includes water from food, not just what you drink.
How to drink
Sipping about a glass at a time, frequently, is absorbed better than drinking a large amount at once, and it is best to drink before you feel thirsty. During exercise, take small amounts every 15-20 minutes; when sweating heavily for a long time, also replace salts (electrolytes).
Cautions
Caffeinated drinks like coffee and green tea have a mild diuretic effect but still count toward hydration in normal amounts. On the other hand, drinking an extreme volume in a short time risks water intoxication, so avoid it. Thirst and urine color (dark yellow signals a shortfall) are useful cues.
How much water should I drink per day?+
EFSA recommends total water intake (food + beverages) of 2.5 L for men and 2.0 L for women. The IOM (USA) sets total water at 3.7 L for men and 2.7 L for women.
Requirements vary by body weight, activity level, age, and climate. Use this calculator for a personalised estimate.
Does water from food count toward my intake?+
The amount calculated here is your beverage target. To find how much you need to drink as fluids, subtract the water you get from food (approximately 400–600 mL).
How much should I drink during exercise?+
Before exercise: 500–600 mL about 2–3 hours beforehand
During exercise: 150–300 mL every 15–20 minutes
After exercise: 150% of body weight lost (e.g., lose 1 kg → drink 1,500 mL)
For sessions longer than 1 hour, include electrolytes (sodium, potassium) with a sports drink.
Do coffee and tea count as water?+
At very high intakes (4+ cups per day), caffeine may affect fluid balance. Count coffee and tea as fluid, but continue drinking water throughout the day as well.
What are signs of dehydration?+
Pale yellow to clear: good hydration
Dark yellow: mild dehydration
Orange to brown: significant dehydration (hydrate immediately)
Other signs include dry mouth, headache, difficulty concentrating, fatigue, and dizziness. During exercise, drink before you feel thirsty — thirst is already a sign of early dehydration.
· EFSA Panel on Dietetic Products. Scientific Opinion on Dietary Reference Values for water. EFSA Journal. 2010;8(3):1459.
· Institute of Medicine. Dietary Reference Intakes for Water. National Academies Press; 2004. (Men: 3.7 L/day, Women: 2.7 L/day total water)
· Sawka MN, et al. ACSM position stand. Exercise and fluid replacement. Med Sci Sports Exerc. 2007;39(2):377-390.
Results are estimates based on EFSA reference values. If you have a heart or kidney condition, or have been instructed by a physician to restrict fluid intake, follow your doctor's guidance rather than this calculator. This tool is for informational purposes only and does not constitute medical advice.
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