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Water intake calculator
How much water should you drink a day?
A good starting point is about 33 ml for every kilogram you weigh, more if you're active or it's hot. For a 70 kg adult that's about 2.3 litres, from every drink, coffee and tea included. Work out yours below.
Your daily goal
2.9 L
About 12 glasses of 250 ml, from every drink and not just water.
- 2.65 L from your weight (33 ml per kg), activity (+350 ml)
- +250 ml: a glass with each strong coffee
Clear the box to use a typical amount instead: 2.7 L for women and 3.7 L for men, from the US National Academies. Food gives you some water too, about a fifth for most people.
Does coffee count toward your water?
Yes. For regular coffee drinkers, a moderate cup hydrates about as well as the same amount of water, and tea does too. The calculator adds a 250 ml glass for each strong coffee or energy drink, up to 750 ml a day, not because coffee dries you out, but because a glass alongside is a good habit. More in does coffee dehydrate you and what counts as water intake.
How to tell you're drinking enough
The NHS advice is simple: drink enough that your pee is a pale straw colour. Dark yellow means drink more. See the full list of signs of dehydration.
Questions, answered
How much water should I drink a day?
About 33 ml per kilogram of body weight is a good start, roughly 2.3 litres for a 70 kg adult, plus about 350 ml if you exercise most days and 500 ml in hot weather. That counts every drink, not just plain water.
Does coffee count as water intake?
Yes. A moderate cup of coffee or tea hydrates about as well as water for people who drink it regularly, so it counts toward your goal. Very strong drinks are worth pairing with a glass of water.
Is 8 glasses a day right?
It's a reasonable rule of thumb, about 2 litres, but your needs depend on your size, activity and the weather. Larger or very active people usually need more, and food supplies around a fifth of your water.
Do I need more water when I exercise?
Yes. Drink before you start, sip during longer sessions and top up after, more in the heat. See how much water to drink during exercise.
Can you drink too much water?
It's rare, but drinking several litres in a short time, especially during long endurance events, can dilute the salt in your blood. Spread your water through the day and let thirst guide you.
Let the app keep count.
Caffeine vs Water does this all day: every drink added up, your usual coffee counted for you, and a heads-up before the one that would cost you sleep. For iPhone and Apple Watch, free in beta.
Needs an iPhone with iOS 26 or later. We pass your email to Apple to send the TestFlight invite. Privacy