A hydration calculator that shows its work

Most water intake calculators give you a single number and a "Calculate" button, then move on to selling you something. We built Daily Water Intake Calculator to do the opposite: show every term that goes into your result, update it live as you adjust inputs, and turn the number into something you can actually act on — an hourly drinking schedule for the rest of your day.

The model behind the calculator is documented in full on the methodology page, with every constant sourced to EFSA, U.S. National Academies and ACSM reference material. Nothing is hidden behind a black box.

The site runs entirely in your browser. Your inputs and drink log are stored only in your browser's local storage — nothing is sent to a server, and there is no account or sign-up.