The amount of water a child needs each day depends largely on age. Babies under 6 months don’t need any plain water at all, while a 5-year-old may need up to 5 cups a day. Older kids and teens need even more, especially if they’re active. Here’s a breakdown by age so you know what to aim for.
Babies Under 6 Months: No Water Needed
Infants younger than 6 months get all the hydration they need from breast milk or formula. Giving plain water to a very young baby can be dangerous because their kidneys aren’t mature enough to process it properly. Too much water can dilute sodium levels in the blood and interfere with nutrient absorption. Stick exclusively to breast milk or formula during this stage.
6 Months to 5 Years: A Quick Reference
Once your baby starts eating solid foods around 6 months, small amounts of water can be introduced. The amounts increase steadily as children grow:
- 6 to 12 months: 4 to 8 ounces per day (about half a cup to 1 cup)
- 12 to 24 months: 8 to 32 ounces per day (1 to 4 cups)
- 2 to 5 years: 8 to 40 ounces per day (1 to 5 cups)
These ranges are wide because children differ in size, activity level, and how much fluid they get from food and milk. A small, sedentary 2-year-old on the lower end of the range is perfectly fine. A tall, active 4-year-old in the summer will naturally land closer to the upper end.
School-Age Kids and Teens
After age 5, water needs continue to climb. A general guideline is that kids ages 5 to 8 need about 5 cups of water daily, while children 9 to 12 typically need 7 to 8 cups. Teenagers often need 8 to 11 cups, with older teen boys on the higher end. These numbers include water from all beverages, not just plain water, but plain water should be the primary source.
One easy rule of thumb: encourage your child to drink a glass of water with each meal and snack, and keep a water bottle accessible throughout the day. Most kids will naturally drink enough if water is available and offered regularly.
Water Needs During Sports and Heat
Active kids need significantly more fluid than these baseline numbers. Children don’t regulate body temperature as efficiently as adults, so they’re more vulnerable to heat-related illness during practice or outdoor play.
A good approach is to start hydrating about four hours before physical activity and then drink every 15 to 30 minutes during exercise. After a hard practice or game, an extra 8 ounces helps replace what was lost through sweat. For a teen athlete, a realistic schedule might look like 10 ounces four hours before practice, 6 ounces two hours before, and small sips of about 5 ounces every 15 to 20 minutes during activity. After intense sessions, especially double-practice days in hot weather, adding a recovery drink with some electrolytes and protein (like low-fat chocolate milk) helps with rehydration.
Plain water works well for activities lasting under an hour. For longer or more intense sessions, a sports drink with electrolytes can help, but avoid making it a daily habit since these drinks contain added sugar.
Foods That Count Toward Hydration
Water doesn’t only come from a glass. Many kid-friendly fruits and vegetables are packed with water and contribute meaningfully to daily intake. Cucumbers are 96% water. Watermelon and strawberries are both 92% water. A child who snacks on these foods throughout the day is getting a hydration boost on top of what they drink.
This is especially helpful for picky drinkers. If your child resists sitting down with a glass of water, offering water-rich snacks like melon slices, grapes, or cucumber sticks can help bridge the gap.
What About Milk and Juice?
Milk is an important part of a young child’s diet, but it shouldn’t crowd out water. For toddlers ages 1 to 2, about 2 to 3 cups of whole milk per day is standard. Kids ages 2 to 5 can shift to low-fat milk, with a similar daily amount. If your child is filling up on milk all day, they may not drink enough water or eat enough solid food.
Juice is a different story. Even 100% fruit juice is high in sugar and low in fiber compared to whole fruit. For children ages 1 to 3, no more than 4 ounces of juice per day is recommended. For ages 4 to 6, the limit is 4 to 6 ounces. Older kids and teens should cap it at 8 ounces. Water is always a better default than juice for hydration.
Tap Water, Bottled Water, and Fluoride
Tap water in most U.S. communities contains fluoride at a concentration of about 0.7 mg/L, which helps prevent cavities. If your family drinks mostly bottled water, your child may miss out on this benefit, since many bottled brands don’t contain meaningful fluoride levels. Mention this to your child’s dentist so they can recommend supplements if needed.
There’s one exception for very young children. The EPA recommends that kids 8 and under use an alternative water source if local tap water contains more than 2.0 mg/L of fluoride, because excess fluoride during tooth development can cause white spots or streaks on permanent teeth (dental fluorosis). You can check your local water utility’s fluoride level through the CDC’s My Water’s Fluoride tool. For mixing infant formula, using purified, distilled, or demineralized bottled water some of the time can reduce fluoride exposure while still allowing the convenience of tap water.
Signs Your Child Isn’t Drinking Enough
Children don’t always recognize thirst or remember to drink, so it helps to know what mild dehydration looks like. Early signs include darker yellow urine, a dry or sticky mouth, and fewer trips to the bathroom than usual. In infants, fewer than six wet diapers per day is a red flag, and only one to two wet diapers a day signals more serious dehydration.
Other things to watch for: fewer tears when crying, unusual irritability or sleepiness, and skin that looks wrinkled or doesn’t bounce back quickly when gently pinched. Mild dehydration usually resolves by simply offering more fluids, but persistent signs, especially in a baby or a child who’s vomiting or has diarrhea, warrant a call to your pediatrician.
Practical Tips to Help Kids Drink More Water
Getting kids to drink enough water is often more about habit than willpower. A few strategies that work well: let your child pick out their own water bottle, add slices of fruit for mild flavor, and offer water before they ask for another drink. Keeping a filled cup or bottle at their spot at the table and in their backpack normalizes water as the go-to beverage. For younger kids, small cups they can manage on their own encourage independence and more frequent sipping.
Setting a loose schedule can also help. A glass at each meal, one after school, and one before bed covers most of a school-age child’s baseline needs without making hydration feel like a chore.