Water Zero — Hydration Tracker

Most water apps give everyone the same 2 litres and then guilt you into it. That number comes from nowhere — the "eight glasses a day" rule has no scientific source anyone has ever found. Water Zero starts differently. It works out your goal from your body, and then gets out of the way. YOUR GLASS, DOWN TO ZERO The glass on screen holds what's left to drink today, not what you've already had. Every drink lowers the water. Reach zero and the day is done — no confetti, no "keep it up!", nothing to beat. ONE TAP, NO APP The widget lives on your home or lock screen. Tap it and a glass is logged. You never open the app to record a drink; the app is where you look at history and change your settings. A GOAL THAT'S ACTUALLY YOURS Your target is calculated from your body mass, sex and activity, based on published water-turnover research rather than a round number on a poster. It counts drinks only — roughly a fifth of your water comes from food, and that share is already taken off. Change the number any time. Nothing here is a verdict. EVERY DRINK COUNTS IN FULL Coffee and tea hydrate you. There are no penalties, no "caffeine debt", no half-credit. Log the vessel you actually drink from — glass, mug, thermal flask, sports bottle, shaker, espresso cup — or just type an amount. ZERO OF EVERYTHING ELSE No account. No sign-up. No servers. No analytics. No ads. No subscription. Your data stays on your phone and is never sent anywhere, because there's nowhere to send it. Mis-tapped the widget? Undo the last entry from the main screen. Free forever for logging. That's the whole app.