Water intake calculator
Estimate how much water to drink a day from your bodyweight and how much you exercise. It is a sensible starting guide, not a strict rule, and we will say why.
Water intake calculator
Bodyweight
Exercise today
ABOUT A DAY
3.2 litres
roughly 13 glasses
A starting guide based on ~35 ml per kg, plus a little for exercise. Your real need shifts with heat, illness and what you eat, so let thirst and pale urine be the final word, not a fixed number.
Tick off glasses as you go
forme tracks your water alongside your food and day score, so hydration is one less thing to remember.
How much water should you drink?
A common, defensible estimate is about 30 to 35 ml per kilogram of bodyweight a day, plus a little more for exercise and hot weather. For many adults that lands somewhere around 2 to 3 litres, but the right amount is personal.
The honest version
You do not need to hit an exact figure. Food (especially fruit and veg) contributes water too, and your body is good at telling you what it needs. Let thirst and pale-straw urine be the real guide; the number here is just a sensible target to aim near.
Common questions
- How many glasses of water a day?
- Roughly 8 to 12 standard glasses for most adults, scaling with bodyweight and activity. This calculator turns your weight and exercise into an estimate in both litres and glasses.
- Does coffee and tea count?
- Yes. Despite the old myth, moderate tea and coffee count towards your fluids. So do most drinks and water-rich foods. Plain water is just the simplest, calorie-free option.
- Can you drink too much water?
- Very rarely, but it is possible to overdo it in extreme amounts (hyponatraemia). For almost everyone the risk is drinking too little, not too much. Spread it through the day rather than forcing large amounts at once.