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8 glasses of water a day? Six water myths, checked
Do you really need 8 glasses of water a day?
The 8-glasses rule sticks because it's easy to remember. Eight 250 ml glasses make 2 litres, which happens to sit close to one of the official reference numbers. But it's a rule of thumb, not a measurement of you. Glasses aren't a standard size anyway: a tea glass, a water glass and a big mug hold very different amounts.
The European Food Safety Authority (EFSA) sets adequate intakes for total water: about 2.0 L a day for adult women and about 2.5 L for adult men. Total means everything that reaches you: plain water, other drinks and the water inside your food. The NHS keeps it simpler, with an everyday guide of about 6 to 8 glasses of fluid a day.
So the honest answer is “roughly, and it depends”. A bigger body, a hot day, a long walk or a workout push the number up, and the NHS adds pregnancy, breastfeeding and illness to that list. A cool day at a desk with soup for lunch pulls it down. Eight glasses is a fine place to start, but it isn't a test you pass or fail. Further down, there's a simple way to find your own number.
Do coffee and tea count toward your water intake?
Mostly, yes. The NHS counts water, lower-fat milk and drinks without sugar, tea and coffee included, toward your daily fluid. Caffeine does make you pee a little more, but at everyday amounts that effect doesn't cancel out the water in the cup. If you drink tea from breakfast to bedtime, that's welcome news: those glasses are doing their job, and so are the second and third ones offered when you visit friends.
What deserves a second look is what goes into the cup. Plain tea and coffee carry almost no energy; sugar and milk do. A few drinks from our calorie chart:
| Drink | Serving | Energy |
|---|---|---|
| Black tea, unsweetened | 200 g | 2 kcal |
| Turkish coffee, unsweetened | 70 g | 5 kcal |
| Americano | 240 g | 5 kcal |
| Latte, whole milk | 240 g | 108 kcal |
| Ayran | 200 g | 72 kcal |
| Sugar | 4 g (a level teaspoon) | 15 kcal |
Milky coffees sit in between: a 240 g latte brings fluid and 108 kcal at the same time. So count the tea toward your fluid, and if you take sugar, log the sugar as food. The tea itself barely registers.
Do you only get water from drinks?
No. A real share of your water arrives on a plate, which is exactly why EFSA's numbers cover food and drinks together. Soups, stews, fruit, vegetables and yogurt hold plenty of it, and even cooked rice and pasta soak some up. Watermelon, cucumber and tomatoes are mostly water, and a bowl of soup at the start of a meal is as much a drink as a dish.
That's one more reason a single glass count can't fit everyone. A day of lentil soup, salad and fruit brings more water with it than a day of crackers and toast, and on tables where cacık, ayran and fruit are regulars the gap grows. It also means the part you drink can sit below the EFSA totals and still be in line with them, because your food is quietly making up the difference.
Does thirst mean you're already dehydrated?
That line is everywhere, and it's oversimplified. Thirst is your body's normal, early signal, the way hunger is. It switches on when your fluid balance shifts a little, well before anything is wrong. For most healthy adults, drinking when thirsty and having something with meals covers the day. Feeling thirsty is no reason to panic; a glass of water is the whole answer.
A few situations call for drinking ahead instead of waiting for the signal: hot weather, long walks or sport, a fever or a stomach bug, and older age, when thirst can get quieter. And if a doctor has asked you to limit fluids, that advice comes before any app target or rule of thumb, ours included.
Does drinking more water burn fat?
No. Water has no calories, and drinking extra doesn't melt fat or switch on a hidden fat-burning mode. What water can do is shift the scale a little from day to day, which is why one weigh-in says little and the trend over weeks says much more. Those small swings are mostly food and water passing through, not fat coming or going.
Where water makes a real difference is as a swap. A can of cola (330 g in our chart) is 139 kcal and a 200 g glass of orange juice is 90 kcal; the same glass of water is zero. That's arithmetic, not magic, and it only matters if those drinks are part of your day. If you're curious what your daily calories look like overall, our calorie calculator runs the same maths as the app.
What colour should your urine be?
Not see-through. Pale straw-yellow is a perfectly good sign that you're drinking enough. Darker yellow, especially with thirst, is a nudge to have a glass. Completely clear all day mostly means you've had more than you need, and the extra simply passes through.
More isn't always better. Drinking very large amounts in a short time can upset your body's salt balance. It's rare, but it's the reason “drink as much as you can” isn't advice anyone should follow. Colour also changes with some foods, vitamins and medicines, so treat it as a rough guide, not a score. There's no need to check it every time, either. The goal isn't see-through urine all day; it's a comfortable, steady day.
How can you drink more water without forcing it?
If you often forget to drink, you have plenty of company; it slips away easily on a busy day. Small habits beat willpower here. None of these are rules; pick the ones that fit your life.
- Pair water with things you already do. A glass with each meal, one next to your morning tea, one when you get home.
- Keep it in sight. A bottle on the desk or in your bag gets drunk; one at the back of the fridge gets forgotten.
- Eat some of it. Soup, fruit, salad and yogurt all add water to your day without a single extra glass.
- Let your phone remember. A reminder or two is easier than keeping count in your head, and that's what Doydum's water reminders are for.
- Watch it add up. Logging each glass turns a vague “I should drink more” into a number you can see filling up.
How much water should you drink a day, then?
Start from a number that scales with you, then let the day adjust it. In Doydum, your daily water target is 33 ml for every kg of body weight, rounded to the nearest 50 ml, and never below 1.5 L. It's the same maths as our water intake calculator.
| Body weight | Daily target |
|---|---|
| 40 kg | 1,500 ml (the 1.5 L floor) |
| 50 kg | 1,650 ml |
| 60 kg | 2,000 ml |
| 70 kg | 2,300 ml |
| 80 kg | 2,650 ml |
| 90 kg | 2,950 ml |
| 100 kg | 3,300 ml |
Take 70 kg: 33 × 70 is 2,310 ml, which rounds to 2,300 ml, a little over nine 250 ml glasses. Treat it as a target for what you log, not a minimum to force down. On a hot day or after a long walk you may want more; on a day of soup and fruit, less. If you're pregnant, have a medical condition or are under 18, ask a doctor or registered dietitian. Our guide to how much water you should drink goes deeper.
In the app, Doy is the water meter: he fills up with every glass you log. The home-screen widget shows the same Doy, and its “+ Glass” button adds 250 ml without opening the app. Try it here.
How to track your water in Doydum
- See your daily target Your water target comes from the weight in your plan: 33 ml per kg, rounded to 50 ml, at least 1.5 L.
- Log a glass in one tap On Home's water card, tap 250, 500 or 750 ml, or enter your own amount. A mistaken tap can be undone.
- Watch Doy fill up Doy fills up with every glass you log, so the day's water is visible at a glance.
- Add the home-screen widget Touch and hold an empty spot on your Home Screen, open the menu at the top left, tap Add Widget and search for Doydum.
- Tap + Glass on the widget Each tap adds a 250 ml glass without opening the app. It is saved the next time you open Doydum.
- Turn on water reminders Want a nudge during the day? Switch on water reminders; they're scheduled on your iPhone.
Questions people ask
How much water should I drink a day?
EFSA's adequate intake is about 2.0 L of total water a day for women and 2.5 L for men, counting food and all drinks. Doydum turns your weight into a personal target instead: 33 ml per kg, rounded to the nearest 50 ml, at least 1.5 L. Heat, activity and illness can raise what you need.
Does tea count toward water intake?
Yes, for the most part. The NHS includes tea and coffee among the drinks that count toward your daily fluid, and caffeine's mild effect doesn't cancel out the water in an ordinary cup. Sugar and milk add energy, though, so log those as food if you take them.
Can you drink too much water?
It's possible, though rare. Drinking very large amounts in a short time can upset your body's salt balance. For most healthy adults, drinking with meals and when thirsty is plenty. If a doctor has asked you to limit fluids, follow that advice over any target, including the one in Doydum.
Does drinking water help you lose weight?
Water doesn't burn fat. It has no calories, so if sweet drinks are part of your day, swapping some of them for water lowers the energy you take in, and that's the whole trick. Water also moves the scale a little from one day to the next, so watch the trend, not a single weigh-in.