Water Intake Calculator
Get a daily water target: 35 ml per kilogram of body weight plus about 350 ml for every 30 minutes of exercise, with hot-weather guidance.
Baseline of 35 ml per kilogram of body weight — a standard maintenance-fluid heuristic — plus about 350 ml for every 30 minutes of exercise. In hot weather, or if you sweat heavily, drink more than this. Food and other drinks also supply water.
This tool runs entirely in your browser. Your data never leaves your device — it is not uploaded to any server.
How to use
- 1Choose metric (kg) or imperial (lb) units.
- 2Enter your body weight.
- 3Enter how many minutes you exercise per day.
- 4Read the baseline, the exercise bonus and the combined daily target.
Water Intake Calculator
This calculator starts from the standard maintenance-fluid heuristic used in clinical practice: 35 ml of water per kilogram of body weight each day, before any activity. It then adds about 350 ml for every 30 minutes of exercise to cover sweat losses, and shows the baseline and the exercise bonus separately so you can see where the total comes from.
Enter your weight in kilograms or pounds and your exercise minutes per day. In hot weather, or when you sweat heavily, drink more than the calculated total; food and other drinks supply water too. The result is a general hydration estimate, not medical advice.
Frequently asked questions
Where does the 35 ml/kg rule come from?
It is the classic pediatric-to-adult maintenance-fluid heuristic used across clinical practice (often quoted as 30–35 ml/kg/day for adults). For comparison, the European Food Safety Authority puts adequate total water intake at 2.0 L/day for women and 2.5 L/day for men — including water from food.
Do coffee, tea and food count toward the total?
Yes. Roughly 20–30% of daily water intake normally comes from food, and moderate caffeinated drinks contribute to hydration rather than draining it. The calculated figure is plain-fluid guidance on top of a normal diet, so you do not need to drink the whole amount as plain water.
Is this medical advice?
No — this is a general estimate. People with heart, kidney or liver conditions, and those told to restrict fluids, often need less than the calculated amount: follow your clinician's instructions instead.
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