A daily water target from your weight, activity and climate.
Daily water target
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Ounces
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Cups (8 oz)
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500 ml bottles
A general guideline, not medical advice. Needs vary with health conditions, medications and pregnancy — some conditions require limiting fluid intake, so check with a doctor if that applies to you.
How this works
Base = body weight (kg) × 33 ml
+ 350 ml for every 30 minutes of exercise
+ 500 ml extra in a hot or humid climate
This total includes water from all drinks and food with high water content, not only glasses of plain water.
Thirst, urine colour (pale yellow is a good sign) and energy levels are more reliable day-to-day guides than hitting an exact number.
Needs rise substantially with heat, altitude, fever, and pregnancy or breastfeeding — this calculator only adjusts for exercise and climate.
Where does the 33 ml per kg figure come from?
It is a commonly used general hydration guideline based on average body water turnover, roughly equivalent to the "half your body weight in ounces" rule often quoted for pounds.
Does coffee or tea count toward water intake?
Yes, in normal amounts — the old idea that caffeinated drinks cause net fluid loss is not well supported by evidence. Very high caffeine intake is the exception.
Should I drink more in hot weather?
Yes — sweat losses rise sharply with heat and humidity, which is why this calculator adds a flat extra amount for a hot or humid climate. Increase further during heatwaves or heavy sweating.