Water Intake Calculator
This water intake calculator estimates how much water to drink a day from your weight and how active you are. Enter your weight, pick an activity level, and flag a hot climate, and you'll get a daily target in ounces, cups, liters, and milliliters. It's a healthy-adult ballpark to aim for, not a strict rule, since thirst and your own body are the real guide.
Last updated June 17, 2026 About half your weight in ounces Reviewed by the Calcowa team
Enter a weight above 0.
Based on roughly half your body weight in ounces, plus activity and heat. Food and other drinks count too.
150 lb ÷ 2 = 75 oz + 12 activity = 87 oz
How much water should I drink a day?
There's no single right number, but a handy rule is to drink about half your body weight in ounces, then top it up for exercise and heat. For a 150-pound adult that's roughly 75 ounces as a baseline, plus around 12 ounces for a half-hour workout, landing near 87 ounces, which is close to 11 cups or 2.6 liters. This water intake calculator runs that estimate and shows it in every common unit. Remember that food and other drinks add to the total, so you don't have to drink all of it as plain water, and thirst plus a quick check of urine color tell you a lot about whether you're on track. It's a target to aim at, not a quota, and you'll feel it if you're falling behind.
Estimating for a 150-pound adult
Here's a moderately active 150-pound adult. It's the same path the tool runs for any weight, and you'll see it match the boxes above:
- 1
Halve your weight150 pounds divided by 2 is a 75-ounce baseline.
- 2
Add for activityA 30-minute workout adds about 12 ounces, reaching 87.
- 3
Add for heatIn a hot climate, add a bit more to replace what you sweat.
- 4
Convert the units87 ounces is about 10.9 cups, or 2.57 liters, to sip through the day.
Daily water by body weight
Here's the baseline at half your weight in ounces, before activity, for a range of weights. Add more for exercise and heat, which the calculator does for you, so you won't have to guess at the extra.
| Weight | Ounces | Cups | Liters |
|---|---|---|---|
| 120 lb | 60 | 7.5 | 1.8 |
| 150 lb | 75 | 9.4 | 2.2 |
| 180 lb | 90 | 11.3 | 2.7 |
| 210 lb | 105 | 13.1 | 3.1 |
| 240 lb | 120 | 15.0 | 3.5 |
Frequently asked questions
A common starting point is about half your body weight in ounces, so a 150-pound person aims for roughly 75 ounces, then adds more for exercise and heat. That lands near the often-quoted 8 cups, or more for active people. This water intake calculator works from your weight and activity, but thirst, urine color, and your doctor's advice are better guides than any single number.
Take your weight in pounds and halve it for a baseline in ounces, then add roughly 12 ounces for each 30 minutes of exercise and a bit more in hot weather. So 150 pounds with a moderate workout is about 75 plus 12, near 87 ounces. The tool runs that for you and shows it in cups, liters, and milliliters as well.
It's a rough guide, not a rule. The old 8-by-8 advice, eight 8-ounce glasses, suits many adults but isn't tailored to size, activity, or climate. Bigger or very active people need more, and food and other drinks count toward the total too. Use the estimate as a target, and let thirst and how you feel fine-tune it.
Mostly yes. Despite the old belief that caffeine dehydrates you, the fluid in coffee, tea, and most drinks still counts toward your daily total, and food adds a surprising amount too. Plain water is the cleanest choice since it's calorie-free, but you don't have to hit the whole figure from water alone.
Yes, though it's uncommon. Drinking far more than you need in a short time can dilute blood sodium, a condition called hyponatremia, which is serious. For almost everyone, spreading normal amounts through the day is completely safe. If a doctor has limited your fluids for a heart or kidney reason, follow their guidance over any calculator.
No. This water intake calculator gives a general estimate for healthy adults and isn't medical advice. Your needs shift with health conditions, medication, pregnancy, and activity, and a doctor can set a target that fits you. Treat the number as a helpful ballpark, not a prescription, and check with a professional if you have any concern.
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