How much water you actually need.
Personalised by body size, training, climate, and lifestyle — not the 8-glasses myth.
Daily water
Daily water
3.5L
Glasses (250 ml)
14
Per hour awake
217ml
Across 16 waking hours.
Good to know
Is 8 glasses a day actually the rule?+
It's a rough heuristic, not a medical guideline. Actual needs scale with body size, activity, climate, and caffeine intake. For most adults, 30–35 ml per kg of body weight per day is a better starting point.
Does coffee count as water?+
Partly. Caffeine is a mild diuretic, so we add a little extra water (~250 ml per caffeinated drink) to replace what you lose. At moderate intake, the net effect is close to neutral.
How much more when it's hot?+
In tropical heat and humidity, you can lose 1+ litre of sweat per hour of exertion. We add 500–1000 ml as a baseline for hot/humid climates, then another ~425 ml per 30 min of exercise on top.
