Quick answer
The US adequate intake of total water from drinks and food is about 3.7 L a day for men, 2.7 L for women, 3.0 L in pregnancy and 3.8 L while breastfeeding. An adult man's 3.7 L is 125 US fluid ounces, or 15.6 cups.
Choose a group. The calculator returns the total water intake in litres, fluid ounces and cups.
Related tools: Fat Intake Calculator: Daily fat range from calorie intake. Calorie Calculator: Daily calories to maintain, lose or gain weight.
How to use the Water Intake Calculator
- Choose group: Adult man, Adult woman, Pregnant woman and Breastfeeding woman.
- Press Calculate to see the result, and use Reset to start again.
| Input | What to enter | Allowed values |
|---|---|---|
| Group | Choose one: Adult man; Adult woman; Pregnant woman; Breastfeeding woman | Starts at Adult woman |
Formula and method
Formula
adequate intake of total water from drinks and food: men 3.7 L, women 2.7 L, pregnancy 3.0 L, lactation 3.8 L per day
IEEE-754 double precision; shown to the decimals indicated.
These are population adequate intakes, not personal requirements; climate, activity and health change needs, and about 20% typically comes from food. Informational estimate, not medical advice. Talk to a qualified health professional about your own situation.
Worked examples
These examples are verified: each one is an automated test case that the live calculator must reproduce exactly.
Example 1
Inputs: Group = Adult man.
| Result | Value |
|---|---|
| Total water per day | 3.7 L |
| US fluid ounces | 125 |
| US cups (8 fl oz) | 15.6 |
Example 2
Inputs: Group = Adult woman.
| Result | Value |
|---|---|
| Total water per day | 2.7 L |
| US fluid ounces | 91 |
| US cups (8 fl oz) | 11.4 |
Example 3
Inputs: Group = Pregnant woman.
| Result | Value |
|---|---|
| Total water per day | 3 L |
| US fluid ounces | 101 |
| US cups (8 fl oz) | 12.7 |
The first line is the headline result (total water per day). Below it the water Intake Calculator lists uS fluid ounces and uS cups (8 fl oz), which describe the same case from other angles. IEEE-754 double precision; shown to the decimals indicated.
Drinks and food
About 20% of water intake comes from food, so drinks provide roughly 3 L for men and 2.2 L for women. Tea, coffee and other drinks count.
Needs change
Needs rise with heat, exercise, illness and altitude. Thirst and pale urine are practical guides. Some medical conditions require fluid restriction, so follow clinical advice.
What happens with invalid input
These messages are produced by the calculator itself, so you know what to fix.
- Group: left empty shows "Enter group." beside that field and no result.
Choosing between the Water Intake Calculator and similar calculators
Each row shows what a related calculator on this site asks for and what it returns, so you can pick the one that matches your question.
| Calculator | You enter | It returns |
|---|---|---|
| [Fat Intake Calculator](/health/fat-intake-calculator/) | daily calories | Fat per day |
| [Calorie Calculator](/health/calorie-calculator/) | units, sex and weight | Maintenance calories |
| [Dog Water Intake Calculator](/lifestyle/dog-water-intake-calculator/) | dog's weight | Daily water |
| [BMR Calculator](/health/bmr-calculator/) | units, sex and weight | Basal metabolic rate |
| [TDEE Calculator](/health/tdee-calculator/) | units, sex and weight | Total daily energy expenditure |
Background: nutrition estimates
Nutrition calculators estimate: they use population-average equations and food tables, and different tables give different numbers for the same food. Certain medical conditions change energy needs in ways basic formulas cannot see, and only laboratory analysis gives exact nutrient values.
Use the result as a starting point, track what actually happens over a few weeks and adjust; ask a qualified professional about medical or clinical decisions.
Assumptions and limitations
- Needs rise with heat, exercise and illness
- Not a diagnosis
This calculator gives general information based on published formulas. It is not medical advice, and it cannot account for your health history. Talk to a qualified clinician about decisions that affect your health.
If a required value is empty, not a number, or outside its allowed range, the form marks that field with a message and shows no result instead of a misleading number. The automated checks deliberately try invalid entries for group to confirm this.
Frequently asked questions
How many cups of water per day?
About 9 for women and 13 for men from drinks.
Does coffee count?
Yes, mostly: coffee and tea count toward total water intake, though they contain caffeine.
Can I drink too much?
Rarely, but hyponatraemia is possible.
What does the Water Intake Calculator calculate?
Adequate daily water intake for adults by group. It returns Total water per day, US fluid ounces and US cups (8 fl oz).
What formula does the Water Intake Calculator use?
adequate intake of total water from drinks and food: men 3.7 L, women 2.7 L, pregnancy 3.0 L, lactation 3.8 L per day. These are population adequate intakes, not personal requirements; climate, activity and health change needs, and about 20% typically comes from food.
What do I need to enter in the water Intake Calculator?
You enter Group.
How is the result rounded or limited?
IEEE-754 double precision; shown to the decimals indicated. Needs rise with heat, exercise and illness.
What are the limits of this calculator?
Needs rise with heat, exercise and illness. Not a diagnosis.
What does the “Group” option change?
It sets how the water Intake is worked out. The choices are Adult man, Adult woman, Pregnant woman and Breastfeeding woman.
What is an example of a water Intake result?
With group Adult man, the total water per day is 3.7 L.
Where does the method come from?
The method follows: Institute of Medicine, Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate (2005).
Can I rely on this calculator for a decision?
This calculator gives general information based on published formulas. It is not medical advice, and it cannot account for your health history. Talk to a qualified clinician about decisions that affect your health. For this calculator in particular: Needs rise with heat, exercise and illness.
Related calculators
- Fat Intake Calculator — Daily fat range from calorie intake.
- Calorie Calculator — Daily calories to maintain, lose or gain weight.
- BMR Calculator — Estimate basal metabolic rate with the Mifflin–St Jeor and revised Harris–Benedict equations.
- TDEE Calculator — Total daily energy expenditure from BMR and activity level.
- Protein Calculator — Daily protein target by body weight and activity.
Sources
- Institute of Medicine, Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate (2005)
Content last reviewed 2026-11-04. Formulas and worked examples are checked by automated tests against independently computed values.