Water Intake Calculator
Water Intake Calculator
Find out how much water you actually need a day, based on your weight, your exercise and where you live.
Your body water is a number you can track.
Drinking the right amount is one thing. Knowing how hydrated you really are is another. The ScanFit Body Scanner measures your body water along with your fat and muscle, so you can watch it over time.
See The Body Scanner Estimate My Body FatMost adults need roughly 33 ml of water per kg of body weight a day (about half an ounce per pound), plus about 350 ml for every 30 minutes of exercise, plus more in the heat. About 80% of it should come from drinks. The calculator works out your number.
How We Work It Out
- Baseline: 33 ml per kg of body weight, which is about 0.5 oz per lb.
- Exercise: about 350 ml (12 oz) extra for every 30 minutes you work out.
- Heat: about 500 ml (17 oz) extra if you're hot or sweating a lot most of the day.
- Drinks versus food: roughly 20% of your water comes from food, mostly fruit, vegetables and soups. The rest needs to come from drinks.
For comparison, the US National Academies set total water guidelines of about 3.7 L (125 oz) a day for men and 2.7 L (91 oz) a day for women. Those are for average adults, and your own number from the calculator is more personal.
Why 8 Glasses Is Only A Starting Point
Eight glasses is easy to remember, but your body doesn't care about easy. A bigger person, a harder workout or a hot day all raise your needs. A smaller person who sits at a desk in an air-conditioned office needs less.
You also get water from tea, coffee, fruit, veg and soup. It all counts.
Are You Drinking Enough?
- Pale yellow urine is the simplest sign you're doing fine.
- Dark urine, a dry mouth, headaches or feeling tired can mean you need more.
- Pregnant, breastfeeding or ill? You need more. Ask your doctor.
- Heart or kidney condition? Follow your doctor's advice, not a calculator.
What Your Body Water Says About You
Around half to two thirds of your body is water. Muscle holds a lot of it and fat holds much less, so your body water percentage tells you something about your body composition too. Roughly 50 to 65% is typical for men and 45 to 60% for women.
A bathroom scale can't see any of that. A body composition scan can.
Track Your Hydration, Not Just Your Weight
Step on the ScanFit Body Scanner barefoot, hold the handle, and it reads your body from your hands to your feet, then splits it into body fat, muscle mass, visceral fat and body water. Everything lands in the free ScanFit app, so you can watch your trend week by week.
- Up to 10 people can share one scanner.
- Syncs with Apple Health, Garmin and Health Connect.
- 100 days to try it. Don't love it? Send it back.
“The amount of info you get, it’s much, much more than I expected. The biggest one being hydration level, that was jaw dropping…in a good way.”RSD_MtnBiker, United States · Read on Trustpilot
See The Body Scanner Scanner + Food Scale Bundle
Not for anyone with a pacemaker or another implanted electronic device. If you're pregnant, check with your doctor first.
Frequently Asked Questions
How much water should I drink a day?
A good starting point is about 33 ml per kg of body weight (roughly half an ounce per pound), plus extra if you exercise or it's hot. Around 80% of your total water comes from drinks and the rest from food.
Is 8 glasses of water a day right?
It's an easy rule, but it isn't based on your body. A 55 kg person and a 100 kg person need different amounts, and exercise and heat change it again. Use your own number from the calculator.
How much water per pound of body weight?
About half an ounce per pound a day is a common baseline. A 170 lb person would aim for around 85 oz of total water, then add more for exercise or heat.
Does coffee or tea count toward my water?
Yes. Coffee, tea and other drinks all count toward your fluid intake. Water is still the simplest choice, since it has no added sugar or calories.
Can you drink too much water?
Yes, though it's rare. Drinking very large amounts in a short time can dilute the sodium in your blood, which is dangerous. Sip through the day and let thirst and your urine colour guide you.
How do I know if I'm drinking enough?
Pale yellow urine is the easiest sign. Dark urine, headaches, a dry mouth and feeling tired can mean you need more. People with kidney or heart conditions should follow their doctor's advice instead.
Does drinking more water help with weight loss?
It can help a little. Water with meals can leave you feeling fuller, and it replaces sugary drinks. But it isn't a fat-loss trick on its own.
What is a healthy body water percentage?
Roughly 50 to 65% for men and 45 to 60% for women, though it varies with age and how much fat and muscle you carry. Muscle holds more water than fat, so leaner people usually sit higher.
This calculator is for general information only and isn't medical advice. Fluid needs vary with health, medication, pregnancy and climate. If you have a medical condition, take medication that affects fluids, or have questions about how much to drink, talk to your doctor.