How this estimate works
This calculator uses a common rule of thumb rather than a clinical formula:
- About half an ounce of fluid per pound of body weight as a baseline
- Plus about 12 ounces for every 30 minutes of exercise
- Plus about 16 ounces if you live or work in a hot or humid climate
For comparison, the National Academies of Sciences, Engineering, and Medicine set an Adequate Intake for total water from all drinks and foods of about 15.5 cups (3.7 liters) per day for men and about 11.5 cups (2.7 liters) per day for women. Roughly 20% of daily water typically comes from food.
Signs you may need more fluids
- Dark yellow urine, or urinating less often than usual
- Thirst, dry mouth, headache or fatigue
- Feeling dizzy or lightheaded, especially during exercise or in the heat
Pale yellow urine is generally a sign that you're drinking enough.
Water and weight management
Choosing water instead of sugar-sweetened drinks is one of the simplest ways to cut extra calories. Some people also find that drinking water with meals helps them feel full. Learn more in our healthy weight loss guide.
When to be careful
Drinking far more than your body needs can be harmful. People with kidney, heart or liver conditions, or anyone advised to limit fluids, should follow their doctor's guidance rather than this estimate.
Important
This calculator provides a general estimate for educational purposes only. It isn't a diagnosis or a personalized medical recommendation. Talk with your doctor or a registered dietitian about your individual needs. See our medical disclaimer.