How much water should I drink per day?

A common general guideline is about 35 ml of fluid per kilogram of body weight, plus roughly 500 ml for each hour of exercise. For a 70 kg person doing one hour of exercise that is about 2.95 litres. Needs rise in heat, illness and intense activity.

How is the reminder interval worked out?

It divides your daily target into glasses of the size you set, then spreads those glasses evenly across your waking hours to suggest how often to drink.

Is any data uploaded?

No — all calculations run locally in your browser and nothing is stored.

Hydration Reminder Calculator

Hydration reminder calculator

This tool turns your body weight and activity into a daily fluid target, then spreads it across your waking hours so you know roughly how often to take a drink. The baseline is about 35 ml per kilogram per day, plus extra for exercise.

Enter your weight, exercise time, waking hours and glass size. The result shows your target in litres and a simple drink-every-X-minutes schedule — calculated in your browser. This is a general guideline, not medical advice.