How much water do you need?
The US National Academies set an “adequate intake” of about 3.7 liters (125 oz) of total water a day for men and 2.7 liters (91 oz) for women. That includes water from all drinks and food — food usually provides about 20%.
This calculator uses a popular rule of thumb — half an ounce of water per pound of body weight, plus about 12 oz for every 30 minutes of exercise — and adds 10% for hot weather.
Signs you are well hydrated
- You rarely feel thirsty.
- Your urine is pale yellow.
Note: people with heart, kidney or liver conditions may need to limit fluids — follow your doctor’s advice.
Sources & review
- Mayo Clinic: Water — how much should you drink every day?
- National Academies: Dietary Reference Intakes for Water
Checked against these sources on November 10, 2026. Rules and rates can change — always confirm with the official source.
Water Intake Calculator FAQs
Do coffee and tea count?
Yes. Caffeinated drinks still count towards your daily fluids for most people.
Can you drink too much water?
Yes, rarely. Drinking very large amounts in a short time can cause low blood sodium (hyponatremia).
Is my information stored?
No.