How Much Water Should I Drink a Day?
The US Institute of Medicine sets total-water Adequate Intakes of 3.7 L/day for men and 2.7 L/day for women; Europe's EFSA sets 2.5 L and 2.0 L. About 80% comes from drinks, 20% from food.
Quick answer
How Much Water Should I Drink a Day?
The US Institute of Medicine (2004) recommends a total-water intake of 3.7 L/day for men and 2.7 L/day for women, counting all beverages plus the moisture in food - about 20% of which comes from food. Europe's EFSA (2010) sets lower targets of 2.5 L/day for men and 2.0 L/day for women, assuming a moderate temperature and activity.
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There is no single magic number, but two major authorities give clear reference values. The US Institute of Medicine (IOM 2004) recommends a total-water Adequate Intake of 3.7 L/day for men and 2.7 L/day for women, where 'total water' means drinking water plus all beverages plus the moisture in food. From IOM's NHANES data for 19-30-year-olds, beverages and drinking water supply about 81% of total water and food about 19% - so roughly 80% comes from what you drink and 20% from what you eat. Europe's EFSA (2010) sets lower targets of 2.5 L/day for men and 2.0 L/day for women, assuming a moderate environmental temperature and a physical activity level (PAL) of 1.6. These are population averages: needs rise with heat, exercise, pregnancy, and lactation, so treat them as a baseline rather than a personal prescription.
Daily Total-Water Reference Values (IOM 2004 & EFSA 2010)
| Group | Recommendation | Source |
|---|---|---|
| Adult men (IOM) | 3.7 L/day total water (~125 fl oz) | IOM 2004 Adequate Intake for total water (all beverages plus food moisture) for adult men aged 19-70+ years. Source: IOM 2004 DRI Water |
| Adult women (IOM) | 2.7 L/day total water (~91 fl oz) | IOM 2004 Adequate Intake for total water for adult women aged 19-70+ years. Source: IOM 2004 DRI Water |
| Adult men (EFSA) | 2.5 L/day total water (P95 4.0 L) | EFSA 2010 Adequate Intake for adult men, including the elderly. Adolescents aged 14 and over use these adult values. Source: EFSA 2010 Water DRV |
| Adult women (EFSA) | 2.0 L/day total water (P95 3.1 L) | EFSA 2010 Adequate Intake for adult women, including the elderly. Adolescents aged 14 and over use these adult values. Source: EFSA 2010 Water DRV |
| Pregnancy (EFSA) | +300 mL/day above the non-pregnant value | EFSA 2010 additional total-water intake during pregnancy, on top of the adult AI of the same age. Source: EFSA 2010 Water DRV |
| Lactation (EFSA) | +700 mL/day above the non-lactating value | EFSA 2010 additional total-water intake during lactation, on top of the non-lactating AI of the same age. Source: EFSA 2010 Water DRV |
How Much Water by Age (EFSA 2010 Total-Water AIs)
| Age band | Adequate Intake | Source |
|---|---|---|
| Infants 0-6 months | 100-190 mL/kg/day | EFSA 2010 AI for exclusively breast-fed infants aged 0-6 months (expressed per kilogram of body weight). Source: EFSA 2010 Water DRV |
| Infants 6-12 months | 800-1000 mL/day | EFSA 2010 total-water Adequate Intake for infants aged 6-12 months. Source: EFSA 2010 Water DRV |
| Children 1-2 years | 1100-1200 mL/day | EFSA 2010 total-water AI for the second year of life (1-2 years, by interpolation). Source: EFSA 2010 Water DRV |
| Children 2-3 years | 1300 mL/day | EFSA 2010 total-water AI for boys and girls aged 2-3 years. Source: EFSA 2010 Water DRV |
| Children 4-8 years | 1600 mL/day | EFSA 2010 total-water AI for boys and girls aged 4-8 years. Source: EFSA 2010 Water DRV |
| Children 9-13 years | 2100 mL/day (boys), 1900 mL/day (girls) | EFSA 2010 total-water AIs diverge by sex at 9-13 years. From age 14, adult values apply. Source: EFSA 2010 Water DRV |
Adjusting the Baseline for You
Drinks vs Food: the 80/20 split
Both IOM and EFSA count food moisture toward total water. In IOM's NHANES data for 19-30-year-olds, beverages and drinking water supplied about 81% of total water (3.0 L for men, 2.2 L for women) and food the remaining ~19% - so you don't have to drink the entire reference figure.
The ml/kg body-weight rule
A common clinical rule of thumb estimates fluid at about 30 mL/kg/day (often stated as 30-35 mL/kg). getvari's body-weight x 33 mL/kg sits inside that band. It is a heuristic, not an IOM or EFSA value - reviews note it fits poorly for very thin or obese people (Nutrients 2020).
Pregnancy and lactation
EFSA 2010 adds +300 mL/day during pregnancy and +700 mL/day during lactation, on top of the adult Adequate Intake for the same age. These additions reflect the extra fluid demands of carrying and feeding a baby.
Heat and activity
The EFSA AIs assume a moderate temperature and a physical activity level of 1.6. Hotter environments and harder exercise raise sweat losses and your needs, which is why these figures are baselines rather than fixed daily quotas.
Practical Tips for Hitting Your Daily Target
- Use the reference value that fits your region: IOM 3.7 L (men) / 2.7 L (women) in the US, or EFSA 2.5 L / 2.0 L in Europe - both are total water, not just drinks.
- Remember the ~20% from food: fruit, vegetables, soups and yogurt all count toward your total-water intake (IOM 2004).
- If you prefer a body-weight estimate, multiply your weight in kg by ~30-35 mL as a starting point, then adjust - it is a heuristic, not an official value.
- Add EFSA's +300 mL/day in pregnancy and +700 mL/day while breastfeeding above your usual intake.
- Drink more when it is hot or when you exercise: the EFSA figures assume only moderate temperature and activity (PAL 1.6).
- Spread intake across the day rather than front-loading - and let thirst and pale-yellow urine fine-tune the numbers.
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- 3.7 L/day (men) — IOM 2004 Adequate Intake for total water for adult men aged 19-70+ is 3.7 L/day (~125 fl oz).[1]
- 2.7 L/day (women) — IOM 2004 Adequate Intake for total water for adult women aged 19-70+ is 2.7 L/day (~91 fl oz).[1]
- ~81% drinks / ~19% food — Per IOM's NHANES data for 19-30-year-olds, beverages and drinking water supply ~81% of total water intake and food ~19%.[1]
- 2.5 L/day men (P95 4.0 L) — EFSA 2010 Adequate Intake for total water for adult men (including the elderly) is 2.5 L/day, with a 95th percentile of 4.0 L.[2]
- 2.0 L/day women (P95 3.1 L) — EFSA 2010 Adequate Intake for total water for adult women (including the elderly) is 2.0 L/day, with a 95th percentile of 3.1 L.[2]
- 1300 mL (2-3 yr) to 1600 mL (4-8 yr) — EFSA 2010 total-water AIs by age: 100-190 mL/kg/day at 0-6 months, 800-1000 mL/day at 6-12 months, 1100-1200 mL/day in the second year, 1300 mL/day at 2-3 years, 1600 mL/day at 4-8 years.[2]
- 2100 mL boys / 1900 mL girls (9-13 yr) — EFSA 2010 total-water AIs at 9-13 years are 2100 mL/day for boys and 1900 mL/day for girls; from age 14, adult values apply.[2]
- +300 mL pregnancy; +700 mL lactation — EFSA 2010 adds +300 mL/day of total water during pregnancy and +700 mL/day during lactation, above the AI for the same age.[2]
- moderate temp; PAL 1.6 — EFSA 2010 AIs assume a moderate environmental temperature and a physical activity level (PAL) of 1.6.[2]
- ~30-35 mL/kg/day; getvari 33 mL/kg — The body-weight fluid heuristic (~30 mL/kg/day, commonly 30-35 mL/kg) is a clinical rule of thumb, not an IOM/EFSA value; getvari's x33 mL/kg sits within that band.[3]
- >=2.0 L men / >=1.6 L women (older adults) — ESPEN's age-aware older-adult fluid/beverage targets are at least 2.0 L/day for men and at least 1.6 L/day for women.[3]
- [1]IOM 2004 DRI Water — Institute of Medicine (US) Panel on Dietary Reference Intakes for Electrolytes and Water. Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate. Washington, DC: National Academies Press; 2005 (report released Feb 2004). Chapter 4: Water.
- [2]EFSA 2010 Water DRV — EFSA Panel on Dietetic Products, Nutrition, and Allergies (NDA). Scientific Opinion on Dietary Reference Values for water. EFSA Journal 2010;8(3):1459 [48 pp.]. Question No EFSA-Q-2008-464, adopted 4 December 2009.DOI: 10.2903/j.efsa.2010.1459
- [3]Nutrients 2020 fluid review — Masot O, Miranda J, Lavedán A, et al. Fluid Intake Recommendation Considering the Physiological Adaptations of Adults Over 65 Years: A Critical Review. Nutrients. 2020;12(11):3383.PMID: 33158071DOI: 10.3390/nu12113383
Last reviewed: 2026-06-20. Every figure on this page is sourced to the named primary references above.
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Frequently Asked Questions
How much water should I drink a day?
Authorities express daily needs as total-water Adequate Intakes (all beverages plus the moisture in food). The US Institute of Medicine (2004) recommends 3.7 L/day for men and 2.7 L/day for women. Europe's EFSA (2010) sets lower targets of 2.5 L/day for men and 2.0 L/day for women, assuming a moderate temperature and physical activity level of 1.6. These are population averages; needs rise with heat and exercise.
Does that 3.7 L or 2.7 L include water from food?
Yes. Both IOM (2004) and EFSA (2010) define total water as drinking water plus all beverages plus the moisture in food. In IOM's NHANES data for 19-30-year-olds, beverages and drinking water supplied about 81% of total water (3.0 L for men, 2.2 L for women) and food about 19% - so roughly 80% comes from what you drink and 20% from what you eat.
Why are the IOM and EFSA numbers different?
They are two separate authorities with different methods and assumptions. The US Institute of Medicine (2004) sets total-water Adequate Intakes of 3.7 L/day for men and 2.7 L/day for women. The European Food Safety Authority (2010) sets lower values of 2.5 L/day for men and 2.0 L/day for women (with 95th-percentile figures of 4.0 L and 3.1 L), assuming a moderate environmental temperature and a physical activity level of 1.6.
Is the 'drink your body weight in ml' rule legit?
The body-weight rule of about 30 mL/kg/day (commonly stated as 30-35 mL/kg) is a clinical heuristic, not an official IOM or EFSA reference value - neither body expresses adult water needs per kilogram. getvari's body-weight x 33 mL sits within that 30-35 mL/kg band. It is a useful estimate, but reviews note it fits poorly for very thin or obese people (Nutrients 2020); needs also vary with heat, exercise, and health.
How much water should children drink by age?
EFSA (2010) sets total-water Adequate Intakes by age: 800-1000 mL/day at 6-12 months, 1100-1200 mL/day in the second year, 1300 mL/day at 2-3 years, 1600 mL/day at 4-8 years, and at 9-13 years 2100 mL/day for boys and 1900 mL/day for girls. From age 14, adult values apply. These figures include water from food.
Do I need more water during pregnancy or breastfeeding?
Yes. EFSA (2010) recommends an additional 300 mL/day of total water during pregnancy and an additional 700 mL/day during lactation, each on top of the adult Adequate Intake for a woman of the same age (2.0 L/day). These additions reflect the extra fluid demands of pregnancy and milk production.
How much more should older adults drink?
EFSA's adult Adequate Intakes (2.5 L/day men, 2.0 L/day women) apply to the elderly too. ESPEN, the only major guideline that accounts for age, recommends a minimum fluid/beverage intake of at least 2.0 L/day for older men and at least 1.6 L/day for older women (Nutrients 2020).
Should I drink more in hot weather or when exercising?
Yes. The EFSA Adequate Intakes assume only a moderate environmental temperature and a physical activity level of 1.6, so heat and harder exercise push your needs above these baselines. The IOM and EFSA figures are starting points; let sweat losses, thirst, and pale-yellow urine guide how much extra you drink.
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