How the estimate is calculated
Example: 70 kg, 30 minutes of exercise, mild climate: 2,310 ml + 360 ml ≈ 2.7 liters per day.
How this compares with official guidance
Official reference values are given for total water — from drinks *and* food:
| Source | Women | Men |
|---|---|---|
| European Food Safety Authority (2010) | 2.0 L/day | 2.5 L/day |
| US National Academies (2005) | 2.7 L/day | 3.7 L/day |
Food typically provides around 20–30% of total water, so the amount you need to drink is lower than these totals. FitNumbra’s result is an estimate of fluid from drinks.
Simple ways to check your hydration
- Your urine is pale yellow for most of the day.
- You rarely feel very thirsty.
- You drink more around exercise, in hot weather and when you are unwell with fever, vomiting or diarrhoea.
Can you drink too much water?
Yes, although it is rare. Drinking very large amounts in a short time — for example during long endurance events — can dilute sodium in the blood (hyponatraemia). During long events, drink to thirst and consider fluids with electrolytes.
Frequently asked questions
How much water should I drink a day?
Many adults need roughly 1.5–3 liters of fluid from drinks per day, depending on body size, activity and climate. The calculator gives a personal estimate.
Is 8 glasses a day right?
Eight glasses (about 2 liters) is a reasonable general guide for many people, but it is not a scientific rule. Larger or more active people usually need more.
Do coffee and tea count?
Yes. Although caffeine has a mild diuretic effect, caffeinated drinks still contribute to your daily fluid intake for regular drinkers.
Should I drink more when exercising?
Yes. You lose fluid through sweat, so drink before, during and after exercise, especially in hot conditions.
Methods and sources
- EFSA Panel on Dietetic Products, Nutrition and Allergies. Scientific Opinion on Dietary Reference Values for water. EFSA Journal 2010;8(3):1459.
- National Academies — Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate (2005)
Content reviewed: by the FitNumbra editorial team.