Water Intake Calculator

It starts from a baseline for your sex (2000 ml for men, 1600 ml for women, 1800 ml if you prefer not to say), each anchored to a reference body weight. It adds about 12 ml per kilogram above or below that reference, then fixed amounts for your activity level (up to 600 ml) and climate (up to 500 ml for hot weather), plus 300 to 700 ml for pregnancy or breastfeeding. The total is kept between 1500 and 4000 ml and rounded to the nearest 50, matching the goal the Brim app sets on your first day.

Not really. The bodyweight-over-2-in-ounces rule ignores activity, climate and sex entirely, and it assumes only plain water counts. Two people of the same weight can have very different real needs depending on how active they are and how hot it is where they live.

Mostly yes. Research on the Beverage Hydration Index shows coffee, tea and milk all hydrate you, just not always at the same rate as plain water. In the Brim app, Premium subscribers get automatic credit for non-water drinks; the free tier tracks plain water only.

Yes. Heat and humidity increase fluid loss through sweat, so the goal adds up to 500 ml for a hot climate and 250 ml for a warm one. Cold climates add a smaller amount too, since dry heated air and higher respiratory water loss both raise needs even when you are not sweating.

Yes. It runs entirely in your browser. Your weight and the rest of your answers never leave your device, there is no account, and nothing is uploaded or stored.