Focus & productivity
Water intake calculator
Enter your weight and how much you move each day to estimate a daily water target in millilitres.
Food and other drinks also count toward your fluids, so you rarely need to hit this entire number from plain water alone.
How much water you actually need
There is no single right number, but body weight and activity give a useful estimate. This calculator starts from roughly 33 millilitres per kilogram of body weight and adds extra for the fluid you lose while active. A 70 kilogram person doing half an hour of movement lands near two and a half litres a day, which lines up well with common guidance.
Remember that this is total fluid, not plain water. Tea, coffee, milk and the water in fruit and vegetables all contribute, so the glass-by-glass total you need to pour is smaller than the headline figure.
Staying hydrated through the day
Spread your intake rather than gulping it all at once, and lean on simple cues.
| Signal | What it suggests |
|---|---|
| Pale yellow urine | Well hydrated |
| Dark yellow | Time for a drink |
| Thirst | A reliable everyday prompt |
Keep a bottle within reach, drink a glass with each meal, and top up before and after exercise. On hot days or at altitude you will need more. There is such a thing as too much water, so there is no need to force litres beyond comfort.
Frequently asked questions
Does coffee or tea count toward my intake?
Yes. Despite the old myth, moderate caffeine does not dehydrate you, and these drinks contribute to your daily fluids. Water in food counts too, so your target is total fluid, not plain water.
Should I drink more on active days?
Yes. You lose fluid through sweat, so add water around exercise and in hot weather. This calculator already adds an amount for your active minutes, but drink to thirst on heavy days.
Can I drink too much water?
In rare cases, very large amounts in a short time can dilute blood sodium. For everyday life this is unlikely. Spread your intake out and there is no need to force fluids past comfort.