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How much water should I drink a day?

Most adult women need roughly half their body weight in ounces as a starting point, adjusted up for activity, hot climates, alcohol, and caffeine. This tool calculates your personal number in under a minute.

Is the half-body-weight rule medically accurate?

It's a widely used estimate, not a clinical formula. We cross-check it against the National Academies' Adequate Intake benchmark on our methodology section, and this tool is a general estimate — not medical advice.

How much water should I drink while pregnant or nursing?

The National Academies' guidelines suggest a higher total water intake during pregnancy (~101 oz/day) and lactation (~128 oz/day) versus ~91 oz for a non-pregnant adult woman. This tool adds a simplified allowance for pregnancy/nursing — always check your specific needs with your OB/midwife.

Does caffeine dehydrate you?

The diuretic effect of caffeine is mild and inconsistent in people who drink it regularly — it's a minor factor, not a major penalty, in this calculator.

Do you store my data?

No. Everything calculates in your browser. Nothing is saved unless you choose to email yourself a result.

What is a Hydration Personality?

A fun, deterministic label (like The Waterfall or The Camel) based on your own inputs — never random, always traceable to your own answers.

What if I have a kidney, heart, or fluid-restriction condition?

This calculator isn't built to estimate a safe fluid target for that — please check the box on the input screen and talk to your doctor instead of using our number.

Water Intake Calculator

Skip the "8 glasses" myth. Get your real number.

Free · no email needed

Most water calculators quietly run the same half-body-weight formula behind a locked wrapper. This one shows every adjustment — activity, climate, caffeine, alcohol, life stage — as its own line, so you can see exactly how your number was built.

Your details

Weight

No default on purpose — enter yours to see a number.

Activity level

Climate

Caffeine (cups/day)

0 cups

Alcohol (drinks/day)

0 drinks

Life stage

I have a health condition that affects how much fluid I should drink (e.g. kidney, heart, or a fluid-restriction diagnosis)

enter your weight to see your target

Let's check with your doctor first

Kidney, heart, and fluid-restriction conditions change how much you should drink in ways a general calculator can't safely estimate.

We're not going to guess a number here — please talk to your doctor or care team about the right fluid target for you.

Everything else on this page (activity, climate, caffeine, alcohol, life-stage info) still works fine for someone without a condition like this — uncheck the box above if it doesn't apply to you.

YOUR DAILY WATER TARGET

0 oz

0.0 L · 0 cups

Caffeine's diuretic effect is mild and mixed in people who drink it regularly — this is a small allowance, not a penalty.

YOUR HYDRATION PERSONALITY IS...

💧

The Sipper

Your weekly water tracker

(0 oz/day)

each box = 8 oz · boxes per row = your daily goal

How we calculate your number

We start with a common rule of thumb — half your body weight in ounces — then adjust it for the things that actually change how much you need: activity, climate, caffeine, alcohol, and pregnancy/nursing.

This is different from (and simpler than) the U.S. National Academies of Sciences' Adequate Intake (AI) figures, which put total water intake for the average adult woman at about 91 oz a day — but that 91 oz figure includes roughly 20% that typically comes from food, not beverages. So think of our number as an estimate of your beverage share, not a claim that you must drink a lab-derived total from a cup. Pregnancy (+12 oz) and nursing (+32 oz) are simplified add-ons approximating the Academies' published increases for those life stages (~101 oz and ~128 oz respectively, total water, vs. ~91 oz baseline) — not an exact recomputation of those figures.

Activity adjustments approximate the American College of Sports Medicine's fluid-replacement guidance (about +12 oz per 30 minutes of moderate-or-higher exercise).

This tool gives a general estimate, not medical advice. If you have a kidney, heart, or fluid-restriction condition, or you're pregnant/nursing and unsure what's right for you, talk to your doctor or care team.

Sources: National Academies of Sciences, Engineering, and Medicine, Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate (2005); American College of Sports Medicine, "Exercise and Fluid Replacement" position stand (2007).