Water Intake Calculator

The famous "8 glasses a day" was never based on solid evidence. Needs scale with body size, activity, and climate — and food already provides roughly 20% of your fluids. This calculator gives a weight-based estimate adjusted for exercise.

For most healthy people, thirst plus pale-yellow urine is a better regulator than any app. The exceptions worth knowing: heavy heat or exercise, older adults (blunted thirst), kidney stones, and some medications — cases worth an actual conversation with a provider.