Daily Water Intake Calculator
Choose your age group and sex to see the European Food Safety Authority’s (EFSA) adequate intake of total water per day, the part expected to come from drinks and about how many glasses that is. For an adult woman the value is 2 L, for a man 2.5 L.
- From drinks (about 70–80%)1.4–1.6 L
- In glasses (200 mL)about 7–8 glasses
- From food (about 20–30%)0.4–0.6 L
- TÜBER rule of thumb (35 mL × kg)2.45 L
How it is calculated
EFSA’s 2010 scientific opinion sets “adequate intakes” of water from what healthy groups are observed to drink together with keeping urine at a desirable concentration. The values cover total water (drinks and the water in food): 2 L for adult women and 2.5 L for men; the adult values apply from age 14 and also to older people. In pregnancy 0.3 L is added, in proportion to the higher energy intake, and while breastfeeding about 0.7 L for the water lost in milk. The values hold only at a moderate temperature and moderate physical activity (PAL 1.6); in great heat and hard exercise losses of up to about 8 litres a day must be replaced in suitable amounts, together with the lost salts. Turkey’s national dietary guidelines (TÜBER 2022) use the same values.
Total water = EFSA adequate intake (+ pregnancy/breastfeeding add-on) · From drinks ≈ total × 70–80% · Glasses = drinks ÷ glass sizeTotal water is drinking water, drinks of every kind (tea, coffee, milk and mineral water included) and the water in food. EFSA says it is normally assumed that 70–80% of the total comes from drinks and the rest from food, and that this split is not fixed. The glass size is not an official measure; you choose 200 or 250 mL.- Choose the age group and sex; if you are a woman, say whether you are pregnant or breastfeeding.
- EFSA’s adequate intake for your group is taken; +0.3 L is added in pregnancy and +0.7 L while breastfeeding.
- From age 2, 70–80% of the total is shown as the part from drinks, divided by the glass size you chose and rounded to the nearest whole glass.
- For a baby aged 0–6 months the value comes from EFSA’s per-kilogram range and the baby’s weight.
Example
For a breastfeeding woman: 2 + 0.7 = 2.7 L of total water. About 2.7 × 0.70 = 1.89 to 2.7 × 0.80 = 2.16 L comes from drinks; with a 200 mL glass that is 1,890 ÷ 200 ≈ 9 to 2,160 ÷ 200 ≈ 11 glasses.
Frequently asked questions
How many litres of water should I drink a day?
By EFSA, an adult woman’s adequate intake of total water is 2 L a day and a man’s 2.5 L. Usually 70–80% of that comes from drinks; the tool shows that part in litres and glasses. The rest comes from the water in meals, fruit and vegetables.
Is the “8 glasses a day” rule right?
It is not an official rule. TÜBER 2022 recommends that 80% of the recommended total fluid come from water and drinks and puts this as 8–10 glasses, without giving the glass size. The count depends on the glass, so this tool lets you assume 200 or 250 mL.
Do tea, coffee and milk count?
Yes. EFSA’s values cover every kind of drink, drinking and mineral water included, and the water in food. TÜBER 2022 recommends meeting fluid needs mainly with water and limiting sugary drinks.
How is water need worked out from body weight?
EFSA gives no per-kilogram value for adults; its per-kilogram range is only for babies aged 0–6 months (100–190 mL/kg). TÜBER 2022 gives a rule of thumb of 35 mL × body weight per day, and the tool shows that result separately for adults 18 and over, for comparison. The rule is not an EFSA value and for heavier people comes out well above it.
How much more should I drink in hot weather or when exercising?
EFSA gives no fixed add-on. It says the values hold at a moderate temperature and moderate activity, and that in great heat and hard exercise losses of up to about 8 litres a day must be replaced together with the lost salts. For long hard exercise or work in the heat, ask a doctor or sports physician for personal advice.
Can drinking too much water be harmful?
Yes, rarely. By EFSA, an adult’s kidneys can pass at most about 1 litre of urine an hour; drinking faster than that can lower blood sodium (hyponatraemia) and cause brain swelling. EFSA says no single upper limit can be set without regard to the person and their surroundings.
Why do some sources say 2.7 and 3.7 litres?
Those are the US Institute of Medicine’s (IoM, 2004) total water values for adult women and men (women 2.7 L, men 3.7 L), which EFSA lists in its comparison table. They are total water too, not just what you drink. This tool uses the EFSA values used in Europe and Turkey.
Source
- EFSA NDA Panel (2010): Scientific Opinion on Dietary Reference Values for water, EFSA Journal 8(3):1459 — Abstract (p. 1); sections 3.1 (p. 20) and 6.1 (p. 36): drinks/food share; 6.4–6.9 (pp. 37–39): age groups, pregnancy, lactation; 6.10 (p. 39) and Conclusions (pp. 39–40): heat/exercise, water intoxication; Table 5 (pp. 28–30): IoM values
- EFSA (2017): Dietary Reference Values for nutrients — Summary report, EFSA Supporting Publications 14(12):e15121 — section 3.5 Water (pp. 20–21) and Table 2 (p. 23)
- Republic of Türkiye Ministry of Health, Turkey Dietary Guidelines (TÜBER) 2022 — Annex 1.4.1 (p. 253): adequate water intakes; p. 15: 80% from drinks, 8–10 glasses, pregnancy/lactation add-ons; section 2.2.7 (pp. 30–31): 35 mL × kg rule, drinks plan, hyponatraemia