How much water a child should drink can be a little tricky. Unlike an adult, children don’t have the same sorts of reserves, and many factors play into what they need. If you live in a really hot climate or your child is very active, he or she may need more water, etc.

Adult water needs are simple

The quick and dirty calculation done for adults, doesn’t apply to kids. FYI, the calculation is to take your weight (in lbs.) and divide it in half to get the number of ounces a day. So 150 lb. person would need roughly 75 oz./day of water. Now there are lots of great exceptions: breastfeeding women need more water, a 400 lb. person doesn’t need 200 oz., etc. If all else fails, at least make sure you get the absolute minimum of 64 oz. of water a day.

Water needs: Infants

This is also simple. Infants in this age group should NOT be getting any extra water. The water that the infant needs should come in the form of breast milk or formula (which has just the right balance of electrolytes). Infants who are given extra “free water” can get “water intoxication” if they get too much water. The most common way this happens is when parents water down formula to make it stretch further. The immature kidneys aren’t working perfectly yet and too much water can essentially dilute the electrolytes. I’ve seen babies have seizures from water intoxication.

Water needs: Age 6 – 12 months

How much water to drink in this age group has a lot to do with how much breast milk or formula the child is taking. Additionally, the child’s overall nutrition, health, and growth play into it as well. The general rule is 0-8 oz. If I have a child that is failing to thrive, I will tell a parent that every oz. that goes into the child’s mouth needs to have good calories (like that from breast milk or formula). If I have a very fat baby, I may push the limit to 8 oz. a day and keep the formula on the low end of what they should be getting. Most infants will consume between 4-8 oz. and be spot on.

Water needs: Age 1 – 8 years

Here’s where a simple rule falls into play. The rule is your child should drink the equivalent of one glass of water (8 oz.) throughout the day in line with their age. So, for example, a 1 year-old child should get about the equivalent of 1 glass of water (8 oz.) throughout the day. A 2 year-old child should get 2 glasses of water (16 oz.), and so on–see the list below for examples. This rule generally stops when the child reaches age 8. Again, if you live in a hot climate or your child is a big athlete, the water need may go up. If your child isn’t growing well, your pediatrician may swap out some of the water for fluids with high caloric content (whole milk, Pediasure, etc.).

1 year old….…1 glass of water a day (8 oz.)

2 year old…….2 glasses of water a day (16 oz.)

3 year old…….3 glasses of water a day (24 oz.)

4 year old…….4 glasses of water a day (32 oz.)

5 year old…….5 glasses of water a day (40 oz.)

6 year old…….6 glasses of water a day (48 oz.)

7 year old…….7 glasses of water a day (56 oz.)

8 year old…….8 glasses of water a day (64 oz.)

9 year old+…  Stop at 8 glasses of water a day (64 oz.)

FYI: Eight 8 oz. cups (64 oz.) equals 2 liters

Water needs: Teenagers

Teens should get a minimum of 64 oz. per day. However, many teens are very active with sports and will require more fluids (some may need as much as 100 oz./day).

General water rules

Keep in mind that these water amounts are general rules of thumb to help give you an idea of where your child should be. There are always exceptions to the rule, and generally if your child is a few ounces off, it’s not the end of the world. Watch how much is coming out of your child. If a child isn’t urinating every 2-4 hours, then chances are the child isn’t drinking enough water.

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About The Author

Dr. Monica Wonnacott

I'm a pediatrician and a mom. I've been doing this doctor thing for 10 years, and love it. I'm known for giving parents the straight scoop without always sugar-coating it. And I believe in educating parents. The more you know, the better care you give your kids.

Dr. Monica Wonnacott, Pediatric Answers ™

I'm a pediatrician and a mom. Pediatric AnswersTM is where parents can get the straight scoop on their child's health, largely based on my experience in the office and at home. I don't diagnose on the site, so please don't ask. These are just my opinions. Use this site as a resource. And trust your parent gut.

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