Water Intake Calculator
Estimate how much water to drink each day based on your body weight and how much you exercise. A practical starting point, not a rigid quota.
How the water intake calculator works
This tool uses a common weight-based guideline of about 33 ml of water per kilogram of body weight, then adds roughly 350 ml for every 30 minutes of exercise to cover extra losses from sweat.
How much water do you really need?
Health bodies avoid a single rule because needs vary. The EFSA suggests about 2 litres a day for women and 2.5 for men from all drinks, and roughly a fifth of your water also comes from food. The old eight glasses idea is a rough floor, not a precise target.
Better signals than a number
Your body is a better guide than any formula. Drink when thirsty, and aim for pale-yellow urine through the day. You need more in heat, at altitude, during exercise and illness, and in pregnancy or breastfeeding, and a little less when it is cool and you are sedentary.
Frequently asked questions
How much water should I drink a day?
A common starting point is about 33 ml per kilogram of body weight, which is roughly 2 to 2.5 litres for many adults, plus more around exercise. The EFSA suggests about 2 litres a day for women and 2.5 for men from drinks. This calculator personalises that to your weight and activity.
How is water intake calculated here?
The tool multiplies your body weight by about 33 ml per kilogram for a baseline, then adds roughly 350 ml for each 30 minutes of exercise. It is a practical guideline, and your real needs shift with heat, activity, and health.
Do coffee and tea count toward water?
Yes. Despite the myth, the mild diuretic effect of normal coffee and tea is outweighed by their water content, so they count toward your daily fluids. Water is still the best default because it has no calories or additives.
Can I drink too much water?
Rarely, but yes. Drinking very large amounts in a short time can dilute blood sodium, a dangerous condition called hyponatremia. For almost everyone, spacing normal amounts through the day and following thirst keeps you safe.
Should I count water from food?
You do not have to. Foods like fruit, vegetables, soup, and yogurt provide roughly a fifth of total water intake, which is already accounted for by these drink-focused guidelines. The number here is water to drink, on top of what you eat.