Units, Weight, Exercise per day
Daily Water Intake Calculator
Estimate a daily fluid target from your weight and how long you exercise.
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How this calculator works
There is no single required amount of water. A widely used rule of thumb for adults is 30 to 35 mL per kilogram of body weight per day, plus extra for exercise. The US National Academies set adequate total water intake (drinks and food combined) at about 3.7 L for men and 2.7 L for women. About 20% of that normally comes from food.
Formula
- Baseline = 30 to 35 mL × body weight (kg)
- Exercise allowance = 350 mL (12 fl oz) per 30 minutes
- 1 L = 33.814 US fl oz; 1 US cup = 236.6 mL
Worked example
70 kg with 30 minutes of exercise
- Units
- Metric (kg, cm)
- Weight
- 70
- Exercise per day
- 30
Result2.5 - 2.8 L per day
About 89 fl oz or 11 cups, including 0.35 L for exercise.
Things to keep in mind
- Heat, altitude, pregnancy, breastfeeding and illness raise needs.
- People with heart, kidney or liver conditions may need to limit fluids. Follow your doctor's guidance.
- For general information only. It is not medical advice; talk to a health professional about your own situation.
Frequently asked questions
Do I really need 8 glasses of water a day?
Eight 8-ounce glasses (about 1.9 L) is an easy-to-remember target, not a scientific requirement. Needs vary with body size, activity and climate, and other drinks and food count too.
Do coffee and tea count toward my water intake?
Yes. Caffeinated drinks have a mild diuretic effect but still add to your total fluid intake.
How can I tell if I am drinking enough?
Pale yellow urine and rarely feeling thirsty are good signs. Dark urine, headaches and tiredness can point to dehydration.
Sources
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Results are estimates based on the values you enter and the published method shown above. They do not replace professional medical, financial or legal advice. Method reviewed October 7, 2026. About this site