Daily target
Aim for the displayed liters across your full day.
Enter your weight
The visible calculator stays focused on weight and unit selection.
Activity and climate can affect hydration.Adjust manually on unusually hot or intense training days.
Use the result
How to use your water result
Adjust when needed
Hot weather and hard training can increase your fluid needs.
Method
Method, result meaning, and common mistakes
This free water intake calculator estimates daily liters from body weight, then shows an approximate count using 250 ml glasses. Use it as your how much water should I drink per day calculator.
How to use it
Use the result as a baseline, then drink more during hot weather, heavy sweating, or long training sessions.
Common mistakes
Do not force all water at once or ignore thirst, urine color, sweat loss, and electrolytes during intense exercise.
Understand deeper
How hydration targets are estimated in practice
When people ask how much water should I drink per day, the most practical answer starts with body weight. A water intake calculator by weight often uses about 30 to 35 ml per kg as a baseline, then adds more for heat, sweat loss, and hydration for exercise. That is why a lighter desk worker and a heavier, highly active person can have very different fluid needs. Your intake can also shift with climate, sodium intake, and whether you are trying to improve appetite control or water intake for weight loss.
Hydration is not only about hitting a number. It is also about checking signs of dehydration such as thirst, darker urine, fatigue, and lower workout performance, then adjusting your intake across the day. The National Academies guidance from 2004 remains a common reference point, listing total daily water from all sources at about 3.7 liters for men and 2.7 liters for women. It also helps answer questions like does coffee count as water intake, because most fluids still contribute to your daily total.
The formula
Water target = body weight (kg) × 30-35 ml per day, then add about 500-1,000 ml per hour of moderate exercise and more in hot weather if sweat loss rises.
Worked example
A 70 kg person using 35 ml/kg starts at 2,450 ml. Add 500 ml for moderate exercise and the daily target becomes about 2,950 ml, or roughly 3.0 liters per day.
Scientific basis
National Academies of Medicine. Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate (2004). Adequate intake is about 3.7 L for men and 2.7 L for women from all sources.
Related calculators
Pair hydration with nutrition
FAQ