Calculate your personalized daily water intake based on weight, activity level, and climate. Most adults need between 2.0 and 3.5 liters per day. Use our free, science-based calculator for an instant personalized answer in seconds.
The "8 glasses a day" rule ignores body weight, activity, and climate. A 55 kg office worker needs very different hydration than a 90 kg athlete training in heat. Our formula uses 33 ml per kg as a baseline, then adjusts for your lifestyle.