“Eight glasses a day” is easy to remember, but it isn’t what the research says. Your needs depend on your size, activity, climate and diet.
The recommendation
The US National Academies set an adequate intake of total water of about 2.7 litres (91 oz) a day for women and 3.7 litres (125 oz) for men. That is total water from all sources.
About four-fifths comes from drinks, including tea and coffee, and about one-fifth from food. Soups, fruit and vegetables are mostly water.
Let thirst guide you
The same report notes that most healthy people meet their needs by drinking when thirsty and having drinks with meals. You need more when:
- it’s hot or humid,
- you exercise or sweat a lot,
- you’re ill with fever, vomiting or diarrhea,
- you’re pregnant or breastfeeding.
A simple personal estimate
The Nutrition Hub uses a common rule of thumb: about 35 ml per kilogram of body weight, plus roughly 500 ml for each hour of exercise. For a 68 kg person on a rest day, that’s about 2.4 litres from drinks and food together.
Easy ways to drink enough
- Start the day with a glass of water.
- Keep a bottle where you can see it.
- Have a glass with every meal.
- Pale yellow urine is a good everyday sign you’re drinking enough.
People with heart or kidney conditions may need to limit fluids, so follow your doctor’s advice.
Track it
The food diary has a water tracker with a one-tap +250 ml button and your own daily goal.
Sources
Informational content only. Not medical advice. Talk to a doctor or registered dietitian about your own needs.