Water Intake Calculator

A simple starting point for daily fluid is about 33 mL per kilogram of body weight. At 70 kg, that is about 2.3 liters. Add 30 minutes of exercise and it rises to 2.7 liters. This calculator adjusts the estimate for exercise, how active you are and the climate.

Here is how it builds the number. It starts at 33 mL per kg. It adds 350 mL for each full 30 minutes of daily exercise, so 45 minutes counts as one block. It adds 150 mL for a moderate lifestyle or 300 mL for an active one, plus 500 mL for a hot or humid climate. The result shows in liters, milliliters, US cups and fluid ounces.

For comparison, the US National Academies set adequate total water intakes of about 3.7 liters a day for men and 2.7 liters for women. That includes water from food, which supplies roughly a fifth of it. Tea, coffee, milk and other drinks all count toward the rest. Your body gives useful signals. Thirst is a reliable guide for most healthy adults. Pale yellow urine usually means you are drinking enough, while dark urine can be a sign to drink more. Needs rise with heat, fever, vomiting or long exercise.

More is not always better. Drinking far more than you sweat out, especially during long endurance events, can lower blood sodium to dangerous levels. If you have kidney, heart or liver problems, follow your doctor's fluid advice instead. To plan your eating as well, try the Calorie Calculator.