Water Intake Calculator

How much water do you need?

A practical rule of thumb is about half an ounce of water per pound of body weight, plus another 12 ounces for every 30 minutes of exercise. This calculator does that math and shows the result in ounces, cups, and liters so you have an easy daily target to aim for.

Things that raise your needs

• Heat and humidity — you lose more through sweat.
• Exercise — already factored in above; add more for long or intense sessions.
• Altitude, caffeine, alcohol, and illness all increase fluid loss.

FAQ

Does coffee or food count?

Yes — food (especially fruit and vegetables) provides roughly 20% of fluid intake, and coffee and tea count too despite their mild diuretic effect. The number here is total fluids, not just plain water. Not medical advice.

How is my daily target calculated?

It uses a common rule of thumb: about half an ounce of water per pound of body weight, plus another 12 ounces for every 30 minutes of exercise. The result is shown in ounces, cups, and liters so you can use whichever measure suits you.

Can I drink too much water?

Yes, though it's rare. Drinking far more than your body needs in a short time can dilute blood sodium, a condition called hyponatremia. Spread intake through the day and let thirst guide you rather than forcing large amounts at once. This tool gives a general estimate, not medical advice.

Should I adjust the number in hot weather or at altitude?

Yes — heat, humidity, high altitude, illness, alcohol, and caffeine all increase fluid loss, so add to the baseline on those days. The calculator's exercise allowance covers workouts, but you may need more during long or intense activity in the heat.

Is this calculator free and private?

Yes — it's free with no sign-up, works on mobile, and runs entirely in your browser, so your weight and activity details are never sent anywhere.