When can babies have water, and how much?

The short answer

Babies can start having a little water at about 6 months. The American Academy of Pediatrics says to begin offering a small amount around then — 4 to 8 oz (½ to 1 cup) a day.¹ Before 6 months, the AAP says babies should have only breast milk or formula, and that extra water isn’t recommended.²

In real life, 4 to 8 oz is a few sips at each meal from a small cup, not a bottle. It supplements milk feeds; it doesn’t replace them.

Can a 9-month-old have water?

Yes. A 9-month-old is well inside the 6-to-12-month window, so the same 4 to 8 oz a day applies.² The AAP gives no separate figure for 9 months, and many babies drink less — a few sips is fine.

The AAP recommends breastfeeding as the sole source of nutrition for about 6 months, with milk continuing alongside solids after that, so water is never the main event.¹ For how the whole day fits together, see how much solid food a baby should eat.

Why not before 6 months?

Young babies get the fluid they need from breast milk or formula. Extra water can also be risky: the CDC names immature kidney function and a strong hunger drive as factors that raise the risk of water intoxication in infants, especially those under 6 months.³ It advises clinicians to discourage parents from giving water, tap or bottled, to infants younger than 6 months.³

The NHS says fully breastfed babies don’t need any water until they start solids.⁴

Where the advice differs

The NHS adds that formula-fed babies under 6 months may need small sips of cooled boiled water in hot weather.⁴ The AAP page we read makes no such exception, and the CDC says supplemental water generally isn’t indicated for healthy infants who aren’t yet eating solids, with a possible exception for formula-fed infants in hot weather.³

We follow the AAP’s simpler rule: no routine water before 6 months. If it’s very hot and you’re worried your baby needs more fluid, ask your pediatrician rather than guessing an amount.

How to offer water

What about juice and cow’s milk?

Neither is a substitute for water. The AAP says infants under 1 year should not drink juice.¹ It lists cow’s milk as none for 6-to-12-month-olds, with whole milk starting at 12 months.¹ The NHS adds that cow’s milk can be used in cooking or mixed into food from around 6 months, but not as a main drink until 12 months.⁴

After the first birthday, water and plain milk become the everyday drinks. See how much water a child should drink and how much milk a toddler should drink.

What if my baby doesn’t like water?

That’s common and nothing to worry about. At this age water is a practice drink: a way to learn to sip from a cup, not a nutrition need. Breast milk or formula is still doing the real work of keeping your baby hydrated.¹

Try again at a different meal, let your baby hold the cup, and don’t push. A baby who takes only a mouthful or two is well within the range, since 4 to 8 oz is an upper guide rather than a target.²

What changes at 12 months?

Around the first birthday, water becomes one of two everyday drinks, along with plain whole milk.¹ The AAP says children aged 1 to 3 need about 4 cups of fluid a day in total, counting both water and milk.² That is a big step up from the 4 to 8 oz of water for babies, which is why the first year is mostly about milk, and about learning to drink from a cup.

Keep in mind that all of these figures vary by individual child, as the AAP notes.² If your baby is growing well and has plenty of wet diapers, you don’t need to measure every sip.

What about water when your baby is sick?

Plain water isn’t the right fluid for a baby with vomiting or diarrhea. The CDC says children in that situation should be given oral rehydration solution instead of plain water.³ Call your pediatrician for what to give and how much — don’t guess an amount for a baby.

If your baby’s stools are hard after starting solids, see baby constipation after starting solids.

When to call your pediatrician

Common questions