How much water you should drink, every day.
Enter your weight, activity level and climate and see your recommended daily water intake instantly, in ounces, cups and liters, plus a plan for spreading it across the day.
Your details
Your body weight in pounds.
How physically active you are on a typical week.
The typical climate you live and exercise in.
The baseline is half your body weight in ounces per day, then about 12 oz is added per 30 minutes of exercise and the total is raised for hot or humid climates. Results update as you type.
What your target means
How activity changes your target
Pacing your intake through the day
Daily water needs by body weight
Every row uses your activity level and climate. The highlighted row is the closest to your current weight.
| Weight | Ounces / day | Cups | Liters |
|---|
Hydration, explained
How Your Water Needs Are Calculated
A common baseline formula is to drink half your body weight in ounces per day. For a 150-pound person, that is 75 ounces. This base amount is then adjusted upward for higher activity levels (exercise increases water loss through sweat) and hot or humid climates. The result is presented in both ounces and liters for convenience.
Why Hydration Matters
Proper hydration supports nearly every bodily function, from regulating body temperature and lubricating joints to transporting nutrients and removing waste. Even mild dehydration (1-2% body weight loss) can impair concentration, mood, and physical performance. Chronic under-hydration is linked to kidney stones, urinary tract infections, and constipation.
Common questions
Is the "8 glasses a day" rule accurate?
The 8 x 8 rule (eight 8-ounce glasses = 64 ounces) is a convenient guideline but not evidence-based. Actual needs vary significantly by body weight, activity level, diet, and climate. A weight-based calculation like this one provides a more personalized recommendation.
Does coffee and tea count toward my water intake?
Yes, caffeinated beverages do contribute to hydration despite having a mild diuretic effect. The water content outweighs the diuretic effect. However, water and herbal teas are the best choices since they contain no calories or additives.
How do I know if I am drinking enough water?
The best indicator is urine color, pale yellow (like lemonade) indicates good hydration. Dark yellow or amber means you need more water. Other signs of dehydration include thirst, dry mouth, fatigue, headache, and decreased urine output.
This calculator gives a general hydration estimate, not medical advice. Drinking far more water than your body can excrete can cause hyponatremia (dangerously low blood sodium), and people with kidney disease, heart failure or on fluid-restricted diets may need much less than a formula suggests. Talk to a doctor about your fluid needs if you have a medical condition, take diuretics, are pregnant or breastfeeding, or train at high intensity in the heat.