Daily Water Intake Calculator by Weight
The standard formula is 35ml of water per kg of body weight per day. At 70kg that is 2.45 litres. At 80kg it is 2.8 litres. At 60kg it is 2.1 litres. Add 500ml for every 30 minutes of moderate exercise. Caffeinated drinks count partially - about 50% of their volume toward daily intake.
Total per Day
2,950 ml
In Litres
2.95 L
Glasses (250ml)
12 glasses
Hourly Schedule
Spread 2.95L across 16 waking hours = 184ml/hour
About 1 glass every hour
| Component | ml/day |
|---|---|
| Base (35ml × 70kg) | 2450 |
| Activity add-on | +500 |
| Climate add-on | +0 |
| Total | 2950 |
Base recommendation: 35ml per kg of body weight. Additional needs for exercise and heat. Coffee and tea count but alcohol does not. Spread intake throughout the day — avoid drinking large amounts at once.
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Common questions about Daily Water Intake Calculator by Weight
Is the 8 glasses of water per day rule accurate?
8 x 250ml = 2 litres, which happens to match the needs of a roughly 57kg sedentary adult. But it ignores body size, activity, climate, and diet. A 90kg person doing manual work in hot weather may need 4+ litres. The 8-glasses rule is a useful starting point, not a precise prescription.
Does tea and coffee count toward water intake?
Yes, despite the diuretic effect myth. Caffeinated drinks do cause slight fluid loss, but you still absorb more water than you excrete. Coffee and tea at normal intake (3-5 cups/day) count as roughly 70-80% of their volume toward hydration. Water, herbal teas, and non-caffeinated drinks count 100%.
What are signs of mild dehydration?
The first sign is dark yellow urine (target pale yellow, like lemonade). Mild thirst, reduced concentration, headache, and slight fatigue follow. By the time you feel noticeably thirsty, you are already 1-2% dehydrated. Drink regularly throughout the day rather than gulping large amounts when thirsty.