How much water do you really need?
There is no single magic number, despite the famous "eight glasses a day." Your needs depend on your size, how much you move, the climate, and your diet. A common starting point is roughly 30–35 ml of water per kilogram of body weight, with more added for exercise and hot weather. That is the approach this calculator uses to give you a sensible ballpark.
Food counts too
You do not have to drink every drop. A good share of your daily fluid comes from food — fruit, vegetables, soups — and from other drinks. The figure here is total fluid, so treat it as a target your whole day works toward, not a stack of glasses you must down on their own.
Signs you might need more
Thirst is the obvious one, but the colour of your urine is a handy everyday check: pale straw is a good sign, while darker usually means top up. On hot days, during illness, or after heavy exercise, your needs rise — listen to your body.
A quick word of caution
This is general information, not medical advice. Some health conditions affect how much fluid is right for you, so if you have kidney, heart or other concerns, follow your doctor's guidance over any calculator.
Frequently asked questions
Does coffee or tea count?
Largely yes. Despite the old myth, moderate caffeine still contributes to your daily fluids.
Can you drink too much water?
Very rarely, but yes — drinking extreme amounts in a short time can be harmful. Spread your intake across the day.
Is this calculator free?
Yes — free, no signup, nothing stored.