The “eight glasses a day” rule has the curious status of being globally famous and scientifically empty. The original suggestion came from a 1945 US Food and Nutrition Board recommendation that calmly noted most of that water comes from food. The food-from-water part got dropped in transmission. The eight-glasses meme was born.

What actually drives hydration

Body weight is the largest factor. A 60-kilogram person and a 100-kilogram person have very different needs and the difference is roughly 1.3 litres per day. Activity is next: every hour of moderate-to-hard training adds roughly 400 to 800 millilitres. Climate matters more than people expect — hot, dry environments push hydration needs up by 20 to 30 percent. Caffeine and alcohol have small effects, smaller than the internet claims.

What an adaptive tracker is doing

It reads your weight, your training, optionally your local weather, and produces a goal that moves day to day. It also paces reminders so they fire when you are behind, not at fixed clock times that ignore your morning meeting. Reminders that fire on a healthy day stop being reminders. They become noise. The smarter system stays quiet on a 1.5-litre lunchtime and gets loud at 6pm if you are 800 millilitres behind.

Signals you are well hydrated

Pale yellow urine before the first cup of coffee. Steady energy at 3pm without a craving for something cold and sugary. Workouts that do not fall apart in the last ten minutes. These beat any tracker number on a given day.

How Enerium does it

The hydration goal is computed from your weight at signup and re-computed when it changes. Logged workouts add to the goal in real time. Reminders escalate only when you are behind a rolling pace target. One-tap logging — 250, 500, 1000 ml — keeps the friction minimal.