Daily Water Intake Calculator
How much water should you drink daily?
A common guideline is ~33 ml per kg of body weight, plus extra for exercise.
How to use
- Enter your weight in kilograms.
- Add daily exercise minutes.
- Get your target in liters and glasses.
About this tool
Thirst, urine color and activity are better real-time guides than any formula.
Calculated locally; nothing uploaded.
How it works
A widely used heuristic puts baseline water need at roughly 30–35 ml per kilogram of body weight per day, counting all sources. For a 70 kg adult that is 2.1–2.45 litres — in line with European guidance of about 2.0 litres/day for women and 2.5 for men from food and drink combined.
Exercise adds on top: around 350–500 ml per 30 minutes of moderate activity, more in heat. The tool adds an exercise adjustment to the weight-based baseline for this reason.
About a fifth of daily water typically comes from food — fruit, vegetables, soups — so the amount to actually drink is less than the total. Thirst, urine colour (pale yellow is the classic sign of good hydration) and climate all shift the real need; treat the number as a starting estimate, not a quota to force down.
Worked examples
Active 70 kg adult: Base: 70 × 33 ml ≈ 2.3 L, plus ~0.4 L for 30 minutes of exercise ≈ 2.7 L total from all sources — roughly 2.2 L as drinks once food water is subtracted.
Sedentary 50 kg adult: Base: 50 × 33 ml ≈ 1.65 L total, about 1.3 L as drinks. Small body, desk job, cool office — needs are modest.
Quick reference
| Body weight | Base need/day | + 30 min exercise |
|---|---|---|
| 50 kg | ~1.65 L | ~2.0 L |
| 60 kg | ~2.0 L | ~2.4 L |
| 70 kg | ~2.3 L | ~2.7 L |
| 80 kg | ~2.6 L | ~3.0 L |
| 90 kg | ~3.0 L | ~3.4 L |
| 100 kg | ~3.3 L | ~3.7 L |
Frequently asked questions
Is 8 glasses a day accurate?
It is a rough average — actual needs scale with body size, climate and activity.
Can you drink too much water?
Yes, overhydration is possible during endurance events; drink to thirst.
Is this medical advice?
No — a general estimate only.
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