Calculate your ideal water intake
How much you should drink depends on your body, your steps, your training and the weather where you are today. This calculator puts them together using European and international guidelines, and shows every step of the working.
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Your location and weather
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Your daily water
How your number was worked out
When to drink it
What to look for on the label
| On the label | What to look for |
|---|---|
| Dry residue / total dissolved solids | Low (50 to 500 mg/L) for daily drinking; mineral-rich (over 1,500 mg/L) only now and then. |
| Calcium and magnesium | Higher is better for bones, muscles and gut movement; magnesium of 50 mg/L or more counts as rich. |
| Sodium | Under 20 mg/L for everyday water; higher can help after heavy sweating. |
| Bicarbonate and sulphate | Support digestion and gut movement; useful while you are adding fibre. |
| Nitrate | As low as possible; under 10 mg/L if the water is used for babies. |
| Fluoride | Avoid daily use above 1.5 mg/L (the label must carry a warning). |
Still or sparkling: the minerals are the same. Rotate two or three waters with different profiles. Read the full guide below.
Why water matters, and how to choose it
Temperature and training
Sweat is how you cool down. Losing around 2% of your body weight in fluid makes training feel harder and can reduce performance.
Blood, kidneys and energy
Water keeps blood volume up, lets your kidneys clear waste and helps prevent headaches and afternoon tiredness.
Digestion
Fibre needs fluid to soften and move food through the gut. When you eat more fibre, drink more water.
Thirst is late
Thirst arrives after you are already a little low, and becomes less reliable after 65. Pale straw urine is the simplest daily check.
The types of water
| Type | What it means (EU rules) |
|---|---|
| Natural mineral water | From a protected underground source, bottled at the source, with a stable mineral content printed on the label. It cannot be treated except to remove unstable elements such as iron. |
| Spring water | Also from an underground source and bottled at the source, but its mineral content does not have to be stable or listed in full. |
| Table or tap water | Treated drinking water. In most of Europe tap water is safe and tested; a filter helps with taste, chlorine or old pipes. |
| Still or sparkling | Carbon dioxide adds bubbles, not minerals. Sparkling water can cause bloating in some people, and sipping it all day can affect tooth enamel slightly; otherwise it hydrates just as well. |
Reading the label in more detail
- Dry residue at 180 °C is the total mineral content. EU bands: very low mineral content under 50 mg/L, low mineral content under 500 mg/L, rich in mineral salts over 1,500 mg/L.
- Calcium: over 150 mg/L may be labelled "contains calcium". Useful if you eat little dairy.
- Magnesium: over 50 mg/L may be labelled "contains magnesium". Supports muscles, sleep and regular bowel movements.
- Sulphate: over 200 mg/L may be labelled "contains sulphate". Magnesium-sulphate waters have trial evidence for easing constipation.
- Bicarbonate: over 600 mg/L may be labelled "contains bicarbonate". Can help digestion and buffer acidity during hard training.
- Sodium: under 20 mg/L may be labelled "suitable for a low-sodium diet". After long or hot sessions, a little more sodium helps you hold on to the water you drink.
- Nitrate: lower is better; for preparing baby food, choose water labelled as suitable for infants (nitrate under 10 mg/L).
- Fluoride: over 1.5 mg/L the label must say the water is not suitable for regular drinking by infants and children under 7.
- pH is mostly a matter of taste: your body controls its own pH, whatever the water.
Rotate your waters
Instead of drinking only one bottle for years, alternate two or three waters with different mineral profiles: for example a low-mineral water for everyday drinking and a magnesium- or calcium-rich water a few times a week. If you have access to a good local spring, use it, as long as it is officially tested and safe to drink.
Questions people ask
- How much water should I drink a day?
- European guidelines set an adequate total water intake of about 2.0 litres a day for women and 2.5 litres for men, about 20% of which comes from food. Steps, training, heat and pregnancy raise it; the calculator above adds these up for you.
- Is sparkling water as good as still?
- Yes, for hydration. The bubbles add carbon dioxide, not minerals. If sparkling water bloats you, choose still.
- What should I look for on a water label?
- The dry residue (total minerals), calcium, magnesium, sodium, bicarbonate, sulphate, nitrate and fluoride. For daily drinking, a low to moderate mineral content with little sodium and nitrate suits most people.
Sources
- European Food Safety Authority. Scientific opinion on dietary reference values for water. EFSA Journal (2010).
- US National Academies. Dietary reference intakes for water, potassium, sodium, chloride and sulfate (2005).
- American College of Sports Medicine. Sawka MN et al. Exercise and fluid replacement: position stand. Med Sci Sports Exerc (2007).
- Hew-Butler T et al. Statement of the Third International Exercise-Associated Hyponatremia Consensus Development Conference. Clin J Sport Med (2015).
- Directive 2009/54/EC on the exploitation and marketing of natural mineral waters (EU).
- Commission Directive 2003/40/EC: constituents of natural mineral waters and labelling (fluoride) (EU).
- World Health Organization. Guidelines for drinking-water quality, 4th edition incorporating the first and second addenda (2022).
- Dupont C, Hébert G. Magnesium sulfate-rich natural mineral waters in the treatment of functional constipation: a review. Nutrients (2020).
- Armstrong LE, Johnson EC. Water intake, water balance, and the elusive daily water requirement. Nutrients (2018).
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These tools give general estimates for healthy adults and are not medical advice. If you are pregnant, breastfeeding, under 18, or have a medical condition, talk to your doctor.
