A 10-month-old should drink about 4 to 8 ounces of water per day. That’s roughly half a cup to one cup, offered in small sips throughout the day rather than all at once. At this age, breast milk or formula still provides the bulk of your baby’s hydration, so water is a supplement, not a replacement.
Why the Amount Is So Small
Eight ounces might sound like almost nothing, but a 10-month-old’s kidneys are still maturing. They can’t flush excess water as efficiently as an adult’s can. Too much water dilutes sodium levels in the blood, a condition that causes irritability, swelling, abnormally low body temperature, and in serious cases, seizures. This happens when total body water increases by roughly 7 to 8 percent or more in a short period, triggering cellular swelling in the brain.
The risk is highest in babies under 6 months, but it still applies at 10 months. Sticking to the 4-to-8-ounce range keeps your baby safely hydrated without overloading their system.
Breast Milk and Formula Do Most of the Work
At 10 to 12 months, most formula-fed babies drink about 6 to 7 ounces of formula every 4 to 6 hours, which works out to three or four feedings per day. Breast milk follows a similar pattern, though exact volumes vary. Both are mostly water by composition, so they cover the vast majority of your baby’s fluid needs. Human milk and infant formula are sufficient to satisfy fluid requirements for infants, which is why water at this stage is more about practice and exposure than actual hydration.
Think of water as a companion to solid food meals. When your baby eats purees, soft finger foods, or mashed table food, offering a few sips of water alongside the meal helps with swallowing and gets them used to drinking plain water. It also contributes a small amount of fluoride if your tap water is fluoridated, which supports developing teeth.
How to Offer Water
By 10 months, most babies can drink from an open cup when you hold it for them. This is a normal developmental milestone for the 10-to-12-month window. You can also use a straw cup or a small training cup. Sippy cups with spill-proof valves work but don’t teach the same oral motor skills as an open cup or straw.
A practical approach: offer 2 to 4 ounces of water with meals, twice a day. You don’t need to measure precisely. A few sips here and there throughout the day add up. If your baby pushes the cup away or seems uninterested, that’s fine. They’re likely getting enough fluid from milk and the water content in their solid foods.
What Not to Give
Fruit juice should not be given before age 1. The American Academy of Pediatrics made this recommendation clear, noting that juice products marketed specifically for infants offer no nutritional value over whole fruit and breast milk or formula. The one exception is when a pediatrician specifically recommends a small amount to manage constipation.
Flavored waters, sweetened drinks, cow’s milk (before 12 months), and plant-based milks are also off the table at this age. Plain water and breast milk or formula are the only drinks your 10-month-old needs.
When Your Baby Might Need More Fluid
Hot weather, fever, vomiting, and diarrhea all increase fluid loss. In these situations, the priority is extra breast milk or formula rather than extra water, since milk replaces electrolytes along with fluid. If your baby is sick and not feeding well, watch for signs of dehydration: fewer than six wet diapers in a day, fewer tears when crying, and a sunken soft spot on the top of the head. Any of these warrant a call to your pediatrician, who may recommend an oral rehydration solution designed for infants.
On hot days when your baby is healthy and feeding normally, you can offer water a bit more frequently between meals. An extra ounce or two beyond the usual range is reasonable, but breast milk or formula should still be the primary source of hydration.
Tracking Whether Your Baby Is Getting Enough
Wet diapers are the simplest indicator. Six or more wet diapers per day means your baby is well hydrated. The urine should be pale yellow, not dark or concentrated. If your baby is active, eating solids well, and producing plenty of wet diapers, their fluid intake is almost certainly adequate, even if they only take a few sips of water at meals. At 10 months, the combination of regular milk feeds and a small amount of water with food covers what they need.