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Water intake calculator

About 20% of the water you take in each day comes from food, which is why the official intake numbers look bigger than what most people drink.

Clinician review pending Updated

How to use it

  1. Step 1Pick your sex and enter your weight.
  2. Step 2Enter your average minutes of exercise a day.
  3. Step 3Choose mild or hot and humid weather, and say whether you take a GLP-1 medicine.
  4. Step 4Read your target in ounces or liters, plus cups and an hourly pace.

The rule of thumb we use

  • Base: half your body weight in ounces (0.5 oz per lb)
  • Exercise: plus 12 oz for every 30 minutes
  • Heat: plus 16 oz in hot or humid weather

Worked example: 180 lb with 30 minutes of exercise in mild weather: 90 + 12 = 102 oz, about 3 liters.

How it compares with official guidance

The National Academies set adequate intakes for total water of about 3.7 liters a day for men and 2.7 liters for women, including water from food. Needs vary a lot with heat, activity and health conditions.

People with heart failure or kidney disease may need to limit fluids; follow your clinician's advice.

On a GLP-1 medicine

GLP-1 medicines can blunt thirst for some people, and vomiting or diarrhea raise fluid needs. The labels warn that dehydration can harm the kidneys. See Staying hydrated on a GLP-1.

Prefer a chart? See Water by weight: precomputed tables for common inputs.

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Common questions

How much water should I drink a day?

Many adults do well with roughly half their body weight in ounces, more with exercise or heat. Pale yellow urine is a simple check.

Does coffee count toward water intake?

Yes. Coffee and tea count toward fluid intake for regular drinkers, though water is still the best default.

Can you drink too much water?

Yes, though it's rare. Drinking very large amounts quickly, especially during long endurance events, can dangerously lower blood sodium.

Why do I need more water on Ozempic or Zepbound?

These medicines can reduce thirst, and stomach side effects can cause fluid loss. Sipping steadily helps prevent dehydration.

Sources

  1. National Academies: Dietary Reference Intakes for Water, Potassium, Sodium, Chloride and Sulfate
  2. DailyMed: FDA prescribing information (search by drug name)

Clinician review pending. Drafted from primary sources and waiting for sign-off by a registered dietitian before launch. Every number is checked against its source. Drug facts are re-checked quarterly, prices monthly and whenever a label changes. How we review · Report an error