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Daily Water Intake Calculator

Calculate how much water to drink per day based on weight, activity level, and climate. Results in liters and glasses.

Sources: EFSA — Dietary Reference Values for Water · NIH — Water, Hydration and Health

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How Much Water Should You Drink Per Day

Water is the most essential nutrient for the human body: it makes up about 60% of body weight and participates in all vital functions. Even mild dehydration (1-2% of body weight) impairs physical and cognitive performance.

How to Calculate Water Needs

The base formula is simple:

Water needs = 30-35 mL x body weight (kg)

Additional amounts are added for:

  • Physical activity: +500-1500 mL depending on intensity
  • Hot climate: +500-750 mL
  • Breastfeeding: +700 mL

Official Recommendations

EFSA (European Food Safety Authority) indicates adequate intake as:

  • Adult men: 2.5 liters total/day (about 2.0 L from beverages)
  • Adult women: 2.0 liters total/day (about 1.6 L from beverages)

These values include water from food, which accounts for about 20-30% of total intake.

Practical Hydration Tips

Do not wait until you feel thirsty: thirst is a late signal of dehydration. Drink regularly throughout the day, about one glass of water every hour. Always carry a bottle with you. Increase intake before, during, and after physical activity.

Urine color is the best indicator: clear and transparent indicates good hydration, dark and concentrated indicates you should drink more.

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Frequently Asked Questions

How much water should you drink per day?▼
EFSA recommends about 2.5 liters of total water per day for men and 2.0 liters for women, including water from food (about 20-30% of total intake). Actual drinking water needs are about 1.5-2.0 liters, but vary based on weight, activity, climate, and health status.
How can you tell if you are drinking enough?▼
Urine color is the best hydration indicator: light and clear urine indicates good hydration, while dark concentrated urine indicates dehydration. Other dehydration signs include thirst (which appears when you are already slightly dehydrated), fatigue, headaches, dry mouth, and decreased concentration.
Can you drink too much water?▼
Yes, overhydration (hyponatremia) is possible but rare. Drinking excessive amounts in a short time can dilute blood sodium, causing nausea, confusion, and in severe cases seizures. This risk mainly concerns endurance athletes who drink too much during races. Under normal conditions, healthy kidneys can handle up to 0.8-1 liter of water per hour.