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Daily Water Intake Calculator
Recommended daily water from weight, activity level, and climate.
How it works
Your base need is set at 33 millilitres per kilogram of body weight, a widely used starting point for adults. An allowance is then added for movement and for heat, because both raise sweat loss. A sedentary day in cool weather therefore needs less than a training day in summer, and the result moves with those two choices rather than giving one fixed number for everyone. The figure is a planning guide for total fluid, and it assumes you are a healthy adult without a medical fluid restriction.
How to read the result
Spread the total across the day instead of drinking it in two large bursts. A practical pattern is a glass on waking, a glass with each meal, and smaller drinks between meals and around exercise. Thirst, urine colour and how you feel in heat are better day-to-day signals than hitting an exact litre count. If your urine is consistently dark, or you feel dizzy or unusually tired in hot weather, increase fluids gradually and seek medical advice if symptoms persist.
One practical tip
Keep a marked bottle at your desk or in your bag. When the day's target is visible, most people drink more evenly and stop relying on memory. Refill it at a fixed point, such as lunch, so a half-finished bottle at evening tells you at a glance whether you are behind.
On very hot days or during long training, add fluids before you feel thirsty and include some salty food or an electrolyte drink, because plain water alone replaces fluid faster than it replaces the salt lost in sweat.