Water Intake Calculator
Estimate your daily water needs from your weight, exercise and climate.
How to use: Enter your weight and how active you are to estimate how much water to drink each day.
How to use the Water Intake Calculator
Water supports digestion, temperature control, joint lubrication and brain function, yet the right amount differs for every person. A simple rule of thumb is about 33 milliliters per kilogram of body weight each day, which equals roughly one ounce per pound of weight.
This calculator starts from that body-weight estimate, adds about 350 milliliters for every 30 minutes of exercise to replace sweat, and adds half a liter if you are in hot weather. The answer appears in liters, US fluid ounces, 250-milliliter glasses and 500-milliliter bottles so you can use whichever is easiest.
Your total includes fluids from all drinks, and around 20% of intake normally comes from food such as fruit, vegetables and soup. Tea and coffee count too. A pale yellow urine color is a handy sign that you are well hydrated.
Spread your intake through the day instead of drinking it all at once. Needs rise during illness with fever, vomiting or diarrhea, and during pregnancy or breastfeeding. Some medical conditions, including kidney and heart problems, require fluid limits, so follow your doctor’s advice if it differs from this estimate.
Frequently asked questions
Do I need eight glasses a day?
The “eight glasses” rule is a rough guide. Your needs depend on your size, activity and climate, which is why this calculator personalises the number.
Does coffee count toward water intake?
Yes. Caffeinated drinks contribute to your total fluid intake, although water is still the best everyday choice.
Can you drink too much water?
Yes, in rare cases. Drinking extreme amounts very quickly can dilute blood sodium. Sip steadily and drink to thirst.