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Water Intake Calculator — How Much Water Per Day

Forget the one-size-fits-all “8 glasses” rule. Enter your weight, activity level, and climate to get a personalized daily water target — in fluid ounces, cups, and liters, plus an easy hourly drinking schedule.

US units first — pounds are the default. Tap kg to enter kilograms instead.
Sedentary = desk job, little exercise. Very active = intense workouts or physical labor.
Heat and humidity make you sweat more, so your target goes up.
Pregnancy and breastfeeding raise fluid needs. Pick the one that applies.
Your daily water target
— fl oz

Enter your weight to see your target.

—
cups
—
liters
—
16.9 oz bottles
Please enter a valid weight greater than zero.

This calculator gives a general hydration estimate based on common guidelines (about half your body weight in ounces, adjusted for activity and heat). It is not medical advice — talk to your doctor about your specific fluid needs, especially if you are pregnant, breastfeeding, or managing a health condition.

100% private

Your weight and answers are used only to compute your result on this page. Nothing is sent or stored anywhere.

No signup

No account, no email, no app to install. Open the page and get your water target instantly.

Free forever

Unlimited calculations with personalized schedules — free with no hidden limits.

How to use the water intake calculator

  1. 1Enter your weight

    Type your weight in pounds (or tap “kg” to switch to kilograms). This sets your baseline, since hydration needs scale with body size.

  2. 2Pick activity and climate

    Choose your activity level, whether you live in hot or humid weather, and pregnancy or breastfeeding if it applies.

  3. 3See your target and schedule

    Get your daily goal in fluid ounces, cups, and liters, plus an hour-by-hour drinking schedule from 7:00 AM to 10:00 PM.

Why use this hydration calculator

Personalized, not generic

The old “8 glasses” rule ignores body size. This calculator starts from your actual weight — about half your pounds in ounces — for a target that fits you.

Adjusts for real life

Workouts, physical jobs, hot summers, pregnancy, and breastfeeding all change how much water you need. Each factor is built into the result.

US units first

Fluid ounces and cups are the headline numbers, with liters alongside — plus how many standard 16.9 oz bottles your target equals.

Hourly drinking schedule

Your daily total is split into an easy hour-by-hour plan from morning to night, so you can sip steadily instead of chugging at bedtime.

Shows its math

A breakdown explains exactly how your target was built — baseline plus each adjustment — so the number never feels like a black box.

Private and instant

Everything is calculated in your browser. No account, no tracking, no waiting — your answers never leave this page.

Water intake FAQs

How is my daily water target calculated?
The baseline is half your body weight in pounds, in fluid ounces (so 150 lb gives 75 fl oz). Then we add 12 fl oz for light activity, 24 for moderate, or 36 for very active; 12 more for hot or humid weather; 10 for pregnancy or 25 for breastfeeding. The total is rounded to the nearest ounce.
Is the “8 glasses a day” rule true?
Not exactly. Eight 8-ounce glasses (64 fl oz) is a decent average, but a 120 lb person and a 250 lb person have very different needs — as do athletes, outdoor workers, and pregnant women. A weight-based target like this one is more accurate than a single number for everyone.
Does coffee or tea count toward my water intake?
Mostly, yes. Caffeinated drinks do have a mild diuretic effect, but research shows they still hydrate you. Count them toward your total, but try to make plain water the biggest share of your fluids.
Can you drink too much water?
Yes, though it is rare. Drinking extreme amounts in a short time can dilute blood sodium (hyponatremia). If you are doing endurance exercise for hours or have a kidney or heart condition, follow your doctor’s guidance rather than pushing past thirst.
What are signs I am not drinking enough water?
Common signs include dark yellow urine, headaches, fatigue, dry mouth, and feeling dizzy when standing up. Pale yellow urine is a good everyday sign you are on track.
Should I drink more water when it is hot outside?
Yes. Heat and humidity raise sweat loss, which is why this calculator adds 12 fl oz for hot or humid climates. On very hot days or during long outdoor workouts, you may need even more — drink to thirst and watch your urine color.
How much water do I need while pregnant or breastfeeding?
Fluid needs rise during pregnancy and rise further while breastfeeding. This calculator adds 10 fl oz for pregnancy and 25 fl oz for breastfeeding on top of your baseline — but always confirm with your doctor, since individual needs vary.
Is this calculator medical advice?
No. It gives a general hydration estimate from widely used guidelines. It does not replace professional advice — check with your doctor about your fluid needs if you are pregnant, breastfeeding, or managing any health condition.

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