Is the water intake calculator free?
Yes. It is completely free to use, with no signup, no account, and no paywall.
Are the results medical advice?
No. The output is a general estimate built from standard formulas and population averages. For decisions about your health, diet, or training, check with a doctor or registered dietitian.
Does it stay local?
Yes. The height, weight, and other details you enter are processed entirely in your browser and never uploaded.
Where does 33 ml per kilogram come from?
It is a widely repeated rule of thumb rather than a guideline from a health authority. Official guidance is given as a flat daily total including food, around 2.0 litres for women and 2.5 litres for men in EFSA's figures, rather than as a per-kilogram formula.
Do tea, coffee, and other drinks count?
Yes. The old idea that caffeine dehydrates you does not survive the evidence at ordinary intakes; a cup of coffee is still a net positive for hydration. Food counts too, which is why any drinking-water-only target is a conservative one.
Can I drink too much water?
Yes, and it is dangerous. Drinking well beyond your needs dilutes blood sodium and can cause hyponatraemia, which has killed marathon runners who over-hydrated during a race. Use thirst and urine colour as the check, not the highest number you can hit.
Should I add water for exercise?
You should, and the calculator will not do it for you. Sweat rates vary enormously, from under half a litre an hour to over two litres in heat. Weighing yourself before and after a session is the practical way to see what you actually lose.
What is the cups figure based on?
A 250 millilitre cup, which is the metric cup. If your glass is 330 ml or your bottle is 750 ml, divide the millilitre figure by that instead, since the cup count is only there to make the target easier to picture.