Blog
Hydration, without the myths.
Short, clear answers about water, coffee, alcohol and electrolytes, with the studies behind them. The same numbers run inside Hydra.
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Daily goal
How much water should I drink for my weight?
About 33 ml per kg (0.5 oz per lb) of drinks a day. A full table by weight in kg and lb, how sex, activity and heat change it, and four worked examples.
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Alcohol
How much water should you drink after alcohol?
How much water offsets a beer, a glass of wine or a shot? Drink-by-drink amounts, worked examples for a night out, and how Hydra works out the water you need.
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Drinks
Does coffee dehydrate you?
No: in normal amounts coffee hydrates about as well as water. What the studies found, where the myth comes from, and how Hydra counts coffee, tea and lattes.
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Myths
Do you really need 8 glasses of water a day?
The 8×8 rule has no scientific origin. What health bodies really recommend, who needs more or less than 8 glasses, and how to find your own daily amount.
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Drinks
Do electrolytes hydrate better than water?
A rehydration drink is kept about 1.5 times better than water, but sports drinks aren't. When electrolytes help, when water is enough, how Hydra counts them.
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Alcohol
Does alcohol dehydrate you? Beer vs wine vs spirits
Yes, but not equally. Why alcohol makes you lose water, how much beer, wine and spirits cost per drink and per ml, and where the factors in Hydra come from.
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Exercise
How much water should you drink when you exercise?
How much water to drink when you exercise: sweat rates, the 2% rule, weighing before and after, when electrolytes help, and how Hydra handles workout days.
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Heat
How much water should you drink in hot weather?
How much water to drink in hot weather: why heat raises your needs, how much extra on a 25, 30 or 35 °C day, and simple habits for keeping up when it's hot.
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Habits
How to drink more water: 10 habits that work
How to drink more water every day: 10 simple habits that work, from knowing your goal and linking drinks to routines to reminders that stop once you're done.
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Drinks
Does milk hydrate better than water?
Yes: milk is kept about 1.5 times as well as water. Why it stays in the body longer, why Hydra counts it ×1.2, and how to log a latte without overcounting.
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Drinks
Does sparkling water hydrate you?
Yes: in a study of 13 drinks, sparkling water hydrated just like still water. What that means for fizzy water, soda and cola, and how to count them in your day.
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Your goal
How much water should you drink when pregnant or breastfeeding?
How much more water you need when pregnant (about +300 ml) or breastfeeding (about +700 ml), examples, and how to set it in Hydra and the water calculator.
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Daily goal
Does food count towards your water intake?
Yes: food gives about 20–30% of your water, but drink goals already leave it out. How much comes from food, and why Hydra's daily goal is for drinks only.
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Apple Watch
How to track your water intake on Apple Watch
How to track your water intake on Apple Watch with Hydra: log a drink in one tap, fix a mistake, add a complication to your watch face, and sync with Health.
Water that counts.
Hydra counts every drink by what your body keeps. Free on iPhone and Apple Watch.
