How much water should you drink a day? There is no single magic number. The NHS suggests 6 to 8 cups or glasses of fluid a day as a guide. European and US guidance ranges from about 2 to 3.7 liters of total water a day, including water from food.
Your own needs depend on your size, how active you are and how hot it is. Pale yellow urine and thirst are simple, practical guides. You need more when you sweat, including during and after training.
Why There Is No Single Daily Water Amount
Water needs vary from person to person and from day to day. A larger person, a hot day or a long sweaty session all increase the amount you lose.
When the US National Academies set its water guidance, the panel said it does not offer a rule of thumb for how many glasses to drink. It noted that most healthy people meet their needs by letting thirst be their guide.
That is why the old fixed rules, such as “8 glasses a day” or a set number of milliliters per kg, are only rough starting points.
Official Daily Water Guidance Compared
Here is what three official bodies say for healthy adults. Note that two of them count water from food as well as drinks.
| Source | Women | Men | What it includes |
|---|---|---|---|
| NHS (UK) | 6 to 8 cups or glasses | 6 to 8 cups or glasses | Fluid from drinks, as a guide |
| EFSA (Europe) | 2.0 liters a day | 2.5 liters a day | Water from all drinks plus moisture in food |
| National Academies (US) | About 2.7 liters a day | About 3.7 liters a day | Total water from drinks and food; about 80% comes from drinks |
These figures are adequate intakes for the general population. They are not targets you must hit exactly every day.
What Counts Toward Your Fluid Intake?
It is not only plain water. The NHS says water, lower-fat milk and lower-sugar drinks, including tea and coffee, all count. Some of your water also comes from food, such as fruit, vegetables, soups and yogurt.
- Best everyday choices: water, lower-fat milk, unsweetened plant drinks, tea and coffee.
- Limit: fruit juice and smoothies to one small glass (150 ml) a day, ideally with a meal, because they are high in sugar.
- Swap: sugary drinks for diet, sugar-free or no-added-sugar versions.
How to Tell If You Are Drinking Enough
The NHS suggests drinking enough during the day that your urine is a pale, clear yellow color. Common signs of dehydration in adults include:
- feeling thirsty
- dark yellow, strong-smelling urine
- peeing less often than usual
- a dry mouth, lips and tongue
- headache, dizziness or light-headedness
- feeling tired
If you notice these signs, drink fluids. If symptoms do not improve, or you feel very unwell, follow the NHS advice on when to get medical help.
How Much Water to Drink Around Training
Exercise raises your needs because you lose water through sweat. Sweat rates vary widely between people. A 2016 joint position statement on nutrition and athletic performance gives a range of 0.3 to 2.4 liters per hour. So your plan should fit you.
Before training
The joint position statement suggests about 5 to 10 ml per kg of body weight in the 2 to 4 hours before exercise. For a 70 kg person, that is about 350 to 700 ml. Aim for pale yellow urine before you start.
During training
For most sessions under an hour, the British Nutrition Foundation says water is the best choice. Keep a bottle with you and sip between sets.
For long or hot sessions, the joint position statement notes that losing more than 2% of your body weight in fluid can harm aerobic performance and thinking. Many people manage with about 0.4 to 0.8 liters per hour, adjusted to their tolerance.
After training
To check your sweat loss, weigh yourself before and after a session. Each kg lost is roughly 1 liter of fluid. To rehydrate, both the joint position statement and the British Nutrition Foundation suggest drinking about 1.25 to 1.5 liters for every kg lost.
Do you need electrolytes?
Sweat contains sodium as well as water. The joint position statement says sodium is worth taking in when sweat sodium losses are large, such as in long, hot or very sweaty sessions. For a typical gym session, water and your normal meals are usually enough.
Can You Drink Too Much Water?
Yes. Drinking much more than you lose through sweat and urine can lower the sodium level in your blood. This is called hyponatremia, and overdrinking is its main cause during exercise. You do not need to force down large amounts. Drink to replace what you lose.
Simple Hydration Habits
- Have a drink with each meal and snack.
- Keep a water bottle at your desk and in your gym bag.
- Drink a little more on hot days and on training days.
- Check your urine color as a quick daily guide.
- Pair drinks with food. A glass of milk with your high-protein breakfast helps with both fluid and protein.
Hydration is one part of healthy eating for strength training. For fuel around sessions, see what to eat before and after a workout. If you log your food, our beginner’s guide to tracking macros explains where drinks fit in.
If you have a heart, kidney or other medical condition, or you have been told to limit fluids, follow your doctor’s advice instead of general guidance.
Stay Hydrated and Keep Training
Water will not build muscle on its own, but it helps you show up ready to train. If you want each session planned for you, 12REPS builds your workouts around your goal, your equipment and the time you have. It also tracks your streaks and weekly goal to help you stay consistent.
Sources
- Water, drinks and hydration. NHS, accessed 2026. https://www.nhs.uk/live-well/eat-well/food-guidelines-and-food-labels/water-drinks-nutrition/
- Dehydration. NHS, accessed 2026. https://www.nhs.uk/conditions/dehydration/
- Summary of Dietary Reference Values, version 4. European Food Safety Authority (EFSA), 2017. https://www.efsa.europa.eu/sites/default/files/assets/DRV_Summary_tables_jan_17.pdf
- Report Sets Dietary Intake Levels for Water, Salt, and Potassium to Maintain Health and Reduce Chronic Disease Risk. National Academies of Sciences, Engineering, and Medicine, 2004. https://www.nationalacademies.org/news/report-sets-dietary-intake-levels-for-water-salt-and-potassium-to-maintain-health-and-reduce-chronic-disease-risk
- Nutrition and Athletic Performance: Position of Dietitians of Canada, the Academy of Nutrition and Dietetics and the American College of Sports Medicine. Dietitians of Canada, 2016. https://www.dietitians.ca/DietitiansOfCanada/media/Documents/Resources/noap-position-paper.pdf
- Sport and exercise. British Nutrition Foundation, accessed 2026. https://www.nutrition.org.uk/creating-a-healthy-diet/sport-and-exercise/
