Water Intake Calculator
How much water do you actually need? Get a personalised daily target based on your weight, activity, climate, and exercise — not the "8 glasses" myth.
Daily water
3.5L / day
Total daily water needs
3.5L / day
12 glasses (250ml each) from drinks
Your daily target (drinks only)
From drinks
2.8L
12 glasses
From food (~20%)
0.7L
Exercise extra
+0.4L
Good news about your 2 cup(s) of tea/coffee: Moderate caffeine intake (3–4 cups/day) does not cause net dehydration. The diuretic effect is offset by the fluid content (Killer et al., 2014, PLOS ONE). Your tea and coffee count toward your daily fluid intake.
The "8 glasses a day" rule has no scientific basis. It likely originated from a 1945 US Food and Nutrition Board report that was taken out of context. Your actual needs depend on body size, activity, climate, and diet (Valtin, 2002, American Journal of Physiology). EFSA recommends 2.5L/day for men and 2.0L/day for women from all sources including food.