Water Intake Calculator

About daily water intake estimates

How much water your body needs depends largely on your body size and activity level, since larger bodies and more physical exertion (which increases fluid loss through sweat) both raise fluid needs. This tool estimates a daily water intake target in liters and cups based on your height, weight, and activity level.

How the estimate is calculated

The tool first estimates your body surface area from height and weight using the Mosteller formula (a standard method in medicine for surface-area-based calculations), then applies a common clinical estimate of about 1500 mL of water per square meter of body surface per day, adding extra fluid for light or active lifestyles to account for sweat loss during physical activity.

Frequently asked questions

Does this include water from food and other beverages, or just plain water?

This estimate represents your total daily fluid needs, which in practice is met partly through food (fruits and vegetables in particular contain significant water) and partly through drinking water and other beverages — it isn't meant to suggest you need to drink this exact amount as plain water alone.

Why does climate or health condition matter, if this tool doesn't ask about them?

This calculator only accounts for body size and general activity level. Hot or humid climates, fever, pregnancy, breastfeeding, and certain medical conditions can significantly increase fluid needs beyond this estimate, so treat the result as a baseline rather than a precise figure for every situation.

Is drinking more water than this target harmful?

For most healthy people, modestly exceeding this estimate isn't harmful since the kidneys excrete excess fluid, but drinking extremely large amounts of water in a short time can be dangerous (a rare condition called water intoxication) — moderation and listening to thirst are generally sufficient.