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Daily water intake calculator
How much water should you drink a day? The most common rule of thumb estimates about 35 ml per kilogram of body weight and adds a little more for each block of exercise. Enter your weight and the minutes of physical activity in the day and get an approximate target in liters, milliliters and cups. It is a practical starting point, not a prescription.
Rule of thumb by body weight
| Weight | Base at 35 ml/kg | With 30 min of exercise |
|---|---|---|
| 50 kg | 1.75 L | 2.25 L |
| 60 kg | 2.10 L | 2.60 L |
| 70 kg | 2.45 L | 2.95 L |
| 80 kg | 2.80 L | 3.30 L |
| 90 kg | 3.15 L | 3.65 L |
How the estimate is made
Water (ml) = weight (kg) × 35 + (exercise minutes ÷ 30) × 500
For a 70 kg person with no exercise, the math gives 70 × 35 = 2,450 ml, or about 2.45 liters. With 60 minutes of activity, two more blocks of 500 ml are added, reaching about 3.45 liters. The value of 35 ml per kilogram is a practical average; some references use a range of 30 to 40 ml per kilogram. The US National Academies of Sciences suggest, as an adequate total water intake, about 3.7 liters a day for men and 2.7 liters for women, counting the water that comes from food, which is close to 20% of the total.
Why it is only a rule of thumb
Real water need varies with climate, altitude, temperature, exercise intensity, pregnancy, breastfeeding, fever and several health conditions and medications. Much of your hydration also comes from fruit, soups, coffee and tea. A simple, reliable sign is urine color: pale yellow usually means good hydration. To plan your whole day, see also the daily calorie calculator and the BMI calculator. Source of the adequate intake reference: National Academies of Sciences, Engineering, and Medicine (formerly the Institute of Medicine).
Disclaimer: an educational rule of thumb. If you have kidney disease, heart disease or any fluid restriction, always follow your doctor's guidance instead of this estimate.
Last updated: · Methodology and sources