Free water intake calculator tells you how much water to drink per day based on body weight and exercise, following the 30-35 ml per kg guideline.
Your daily water need depends mostly on body weight, activity and climate. A common clinical shortcut is 30-35 ml per kg of body weight, plus extra for exercise and heat.
Enter your weight and daily exercise minutes. The result gives your daily target in liters, cups and ounces. For reference, NASEM sets Adequate Intake (total water including food) at 2.7 L for women and 3.7 L for men, while EFSA sets it at 2.0 L for women and 2.5 L for men. Food provides about 20% of total water, so the remaining amount should come from drinks.
A common guideline is 30-35 ml per kg of body weight plus exercise top-up. For example, a 70 kg person starts at about 2.3 L per day.
The NASEM reference includes about 20% from food; the base in this calculator corresponds mostly to beverages, so the two numbers complement each other.
In extreme cases yes, it can cause hyponatremia, especially during endurance events. Adjust by thirst and urine color instead of forcing a fixed amount.
Yes. Moderate caffeine does not meaningfully dehydrate, so coffee and tea can count toward your daily intake.
According to ACSM, about 600-1,200 ml per hour during exercise. This calculator estimates 400 ml per 30 minutes as a practical average.
People with kidney disease need to limit fluids; follow your doctor's instructions. This calculator is not medical advice.
The NASEM reference is 3.7 L per day for men and 2.7 L for women (total water incl. food), mostly because men average larger bodies. This calculator scales with body weight, so the difference is already reflected in your result.