Daily Water Intake Calculator
Staying properly hydrated supports every function in the body - digestion, temperature regulation, joint lubrication and cognitive performance. This calculator gives a personalised daily water target based on your weight and activity level.
How it works
The widely-used baseline is 33 ml of water per kg of body weight per day. Active individuals lose more fluid through sweat, so the activity multiplier increases the target accordingly. These are guidelines - thirst, climate and health conditions also matter.
Daily water (L) = Weight (kg) x 0.033 x Activity factorExample. A 70 kg person with moderate activity needs about 70 x 0.033 x 1.4 = 3.2 litres per day, or roughly 13 glasses.
Frequently asked questions
Does coffee or tea count toward water intake?
Yes - caffeinated drinks do contribute to hydration despite mild diuretic effects. However, plain water is most efficient, and very high caffeine consumption can tip the balance.
Is 8 glasses a day enough?
The 8-glasses rule is a rough approximation. Actual needs depend on body size, activity and climate. Use your weight-based target from this calculator as a better guide.
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