Water Intake Calculator US
Estimate how much water to drink each day based on your body weight and how much you exercise.
General estimate using standard formulas — not medical or dietary advice. For personalised guidance, speak to a qualified professional.
How it works
Enter your body weight and how many minutes you exercise each day. The calculator estimates daily water using about 35 ml per kilogram of body weight, plus extra to replace fluid lost during exercise.
Frequently asked questions
How much water should I drink a day?
A common estimate is about 30–35 ml per kg of body weight, adjusted for activity and climate. The National Academies suggest roughly 3.7 L (men) and 2.7 L (women) from all sources.
Does food and other drinks count toward hydration?
Yes. Water from food — especially fruit and vegetables — and from other beverages all contribute to your daily total.
Does coffee or tea dehydrate me?
Moderate caffeine has only a mild diuretic effect and these drinks still contribute to your fluid intake overall.
How do I know if I am well hydrated?
For most healthy people, drinking to thirst and pale-yellow urine are good practical signs of adequate hydration.
Do I need more water when exercising?
Yes. You lose fluid through sweat, so needs rise during and after exercise and in hot or humid conditions.
Is this medical advice?
No. It is a general estimate. If you have a medical condition affecting fluid balance, follow the guidance of your healthcare professional.
How much water you need
Daily fluid needs vary from person to person, but this tool gives a reasonable estimate based on body weight and activity. A common rule of thumb is roughly 30–35 ml of fluid per kilogram of body weight, which the calculator adjusts for how active you are and your environment.
What changes your needs
You need more fluid in hot or humid weather, at altitude, during and after exercise, and when ill with fever. Body size and diet matter too — and not all of it has to be plain water, since food (especially fruit and vegetables) and other drinks contribute to your total intake.
General guidance
The U.S. National Academies suggest total daily water of roughly 3.7 litres for men and 2.7 litres for women from all food and drink combined, though individual needs differ. For most healthy people, drinking to thirst and keeping urine pale yellow is a simple, practical guide.
When to seek advice
Certain conditions — kidney or heart problems, pregnancy, or medications that affect fluid balance — change how much you should drink, and both too little and too much water can be harmful. Treat this as a general estimate and check with a healthcare professional if you have specific medical concerns.
Results are estimates for general guidance in United States and may not reflect the latest local rates, fees or rules. Check official sources before making decisions.