Water Intake Calculator
This is a general estimate, not medical advice — a sensible starting point for daily hydration, not a precise requirement. It updates instantly, and the link in your address bar always reflects your numbers.
How this calculator works
We start from a commonly-used general guideline of 33 ml of water per kilogram of body weight — this lines up closely with the popular imperial rule of thumb "half your body weight in ounces" (33 ml/kg works out to about 0.51 oz/lb, so the two rules of thumb agree). We then add roughly 400 ml for every 30 minutes of exercise (a conservative pick within the commonly cited 400–700 ml range, since sweat rate varies a lot by person and intensity), and a further 10% on top of your baseline if you selected a hot or humid climate, a reasonable general adjustment rather than a precise clinical figure. This is a general estimate only, not medical advice.
Worked example
A 70 kg person doing 30 minutes of exercise in a temperate climate: baseline is 70 × 33 = 2,310 ml, plus 400 ml for the exercise (30 ÷ 30 × 400), with no climate addition. Total: 2,710 ml — about 91.6 oz or roughly 11.4 cups (using 1 US cup ≈ 237 ml).
Frequently asked questions
Is this the exact right amount of water for me?
No — treat it as a reasonable starting point, not a prescription. Individual needs vary quite a bit based on health conditions, medications, altitude, pregnancy or breastfeeding, and how much you personally sweat. This is a general estimate, not medical advice — if you have a condition that affects fluid balance (like kidney or heart issues), follow your doctor's specific guidance instead.
Does this target include water from food and other drinks?
Guidelines genuinely differ on this point, so we won't overclaim precision. Many official recommendations (like general 'total water intake' targets) are meant to include moisture from food, which typically supplies a meaningful share of daily fluid. In practice, most people use a number like this one as a target for liquids they drink, which naturally builds in some cushion. Either reading is reasonable.
Can I drink too much water?
Yes, though it's rare. Drinking extreme amounts of water in a short time can dilute sodium in your blood, a real condition called hyponatremia (sometimes called water intoxication). It typically takes drinking far beyond normal thirst-driven amounts, often in an endurance-sports context, to become a risk. For everyday hydration, moderation and listening to your thirst are good guides.
Does coffee or tea count toward my water intake?
Generally, yes. The old idea that caffeine causes net dehydration has largely been set aside by current understanding — moderate caffeinated drinks still contribute fluid overall, even with their mild diuretic effect. Water is still the simplest default, but you don't need to mentally subtract your coffee or tea from the total.