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Water intake calculator

Pick your sex and life stage. You see the European and US adequate intakes side by side, how much of that usually comes from drinks, and how many glasses it is.

Updated

Sex

Pregnancy and breastfeeding apply to the female values only.

– L a day in total (EFSA)

NASEM total
–
NASEM from drinks
–
Drinks in glasses
–

Pick your sex to see the reference values.

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Adequate intakes describe healthy people at moderate temperature and activity. Heat, exercise, illness or a medication that causes vomiting or diarrhoea can raise needs; heart or kidney conditions can lower them. Ask your clinician.

The formula this calculator uses

  1. EFSA total (large number)

    women 2.0 · men 2.5 · pregnancy 2.0 + 0.3 = 2.3 · breastfeeding 2.0 + 0.7 = 2.7 litres a day [1]. Men always get 2.5, whatever life stage is selected.

  2. NASEM total and drinks

    women 2.7 total, 2.2 from drinks · men 3.7, 3.0 · breastfeeding 3.8, 3.1 litres a day [2]. Pregnancy is left blank here.

  3. Ounces and glasses

    fl oz = litres × 33.814 · glasses = NASEM drinks (L) × 1000 ÷ glass size (mL).

Worked examples

Each row was entered into this calculator and the result copied as shown.

Water calculator results for four sample entries
EntryEFSA totalNASEM totalNASEM from drinksGlasses
Female · neither · 250 mL glass2.0 L2.7 L · 91 fl oz2.2 L · 74 fl oz8.8
Male · 250 mL glass2.5 L3.7 L · 125 fl oz3.0 L · 101 fl oz12
Female · pregnant · 250 mL glass2.3 L–––
Female · breastfeeding · 237 mL glass2.7 L3.8 L · 128 fl oz3.1 L · 105 fl oz13.1

Reference intakes in one table

Adequate intake of total water, litres a day
GroupEFSA total [1]NASEM total [2]NASEM from drinks [2]
Women2.02.72.2
Men2.53.73.0
Pregnancy2.3 (2.0 + 0.3)see reportsee report
Breastfeedingabout 2.7 (2.0 + 0.6 to 0.7)3.83.1

EFSA values assume moderate temperature and moderate activity (PAL 1.6) [1]. The two bodies used different intake data, which is why their numbers differ.

What this calculator does not do

  • It does not use your weight, activity, climate or health conditions; it shows published values for your sex and life stage.
  • It does not tell you how much to drink, and it is not a fluid limit for heart or kidney conditions.
  • It does not show the NASEM pregnancy value, which we could not read from the source on the day we checked.
  • It does not track what you drink; PepLabo’s water log does that.

About this estimate and your privacy

Adequate intakes are set where evidence is not enough for an exact requirement; they describe what healthy groups usually drink and eat [1][2]. A single person’s needs can be higher or lower.

Everything is worked out by a script inside this page. The script makes no network requests, the page’s security policy (Content-Security-Policy with default-src none and no connect-src) would block them anyway, and nothing you type is stored, not even in your browser’s storage. Reload the page and the fields are empty again.

Next to each source below is what it supports on this page.

Ozempic® is a trademark of Novo Nordisk A/S. Mounjaro® is a trademark of Eli Lilly and Company. PepLabo is not affiliated with or endorsed by them.

Questions

Why do EFSA and NASEM give different numbers?

They are based on different population intake surveys [1][2]. Both describe adequate intakes for healthy groups, not exact requirements, so either is a reasonable reference to talk through with your clinician.

Does this calculator use my body weight?

No. Neither EFSA nor NASEM sets water intake per kilogram [1][2], so this page shows their published values for your sex and life stage rather than a weight-based rule of thumb.

Do coffee, tea and food count?

Yes, in both sets of values. EFSA’s reference covers drinking water, beverages of all kinds and the moisture in food [1]. In the NASEM data, drinks supplied about 81% of total water and food the rest [2].

Do I need more water on a GLP-1 medication?

The labels warn that nausea, vomiting or diarrhoea can lead to dehydration, and that this has been linked to acute kidney injury [3][4]. How much you should drink is a question for your prescriber; the values here describe healthy people.

When should I contact my prescriber about fluids?

The Ozempic® and Mounjaro® labels ask prescribers to tell patients about the risk of kidney injury from dehydration with stomach side effects [3][4]. If you cannot keep fluids down, contact your prescriber.

What about hot weather or exercise?

EFSA’s values only apply at moderate temperature and moderate physical activity (PAL 1.6) [1]. Heat and heavy activity raise needs, which this calculator does not model.

What does EFSA add for pregnancy and breastfeeding?

About 300 mL a day in pregnancy and about 600 to 700 mL a day while breastfeeding, on top of the adult female value [1]. NASEM lists 3.8 L total and 3.1 L from drinks for breastfeeding [2].

Why is there no NASEM value for pregnancy?

We could not read the NASEM pregnancy row from the source on the day we checked, so we leave it blank rather than repeat a number we have not verified. The report is linked below.

Can PepLabo remind me to drink?

Yes. PepLabo logs water with a tap, shows the day’s total and can send water reminders every 1, 2 or 3 hours or spread across your waking hours.

Sources

Sources checked on

  1. EFSA Panel on Dietetic Products, Nutrition and Allergies. Scientific Opinion on Dietary Reference Values for water. EFSA Journal 2010;8(3):1459 Supports: EFSA adequate intakes for women, men, pregnancy and lactation; what total water includes; moderate temperature and PAL 1.6.
  2. National Academies (NASEM). Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate (2005) Supports: NASEM total water and drink amounts for adults and lactation; about 81% from drinks.
  3. Ozempic® (semaglutide) injection: US prescribing information, Novo Nordisk (DailyMed) Supports: dehydration with gastrointestinal reactions and acute kidney injury warning.
  4. Mounjaro® (tirzepatide) injection: US prescribing information, Eli Lilly and Company (DailyMed) Supports: dehydration with gastrointestinal reactions and acute kidney injury warning.

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