Week 21 old
Week 21 of your baby's first year: longer, more predictable wake windows, bigger feeds, and lots of grabbing and rolling. Here's what's typical around 5 months.
In short
At 21 weeks (about 5 months), many babies take 24-32 oz of milk a day, sleep around 14-15 hours total, and stay awake for roughly 2 to 2.5 hours between naps.
🍼 Feeding
Breast milk or formula is still the main nutrition: roughly 24-32 oz of formula a day across about 4-6 feeds, or nursing every 3-4 hours. Most babies aren't quite ready for solids yet — readiness signs (good head control, sitting with support, interest in food) and the green light usually come closer to 6 months. Talk to your pediatrician before starting solids.
😴 Sleep
About 14-15 hours total — typically 3 naps and roughly 10-11 hours overnight, often with night wakings. Wake windows are commonly around 2 to 2.5 hours. Always place your baby on their back to sleep on a firm, flat surface with no pillows, bumpers, blankets, or soft toys.
What's happening this week
- •Around this age, many babies push up on their forearms during tummy time and may roll from front to back, and some begin rolling back to front.
- •Hands are busier now — many babies reach for toys, grab them with the whole hand, and bring nearly everything to the mouth to explore.
- •Babbling often becomes more expressive around now, with cooing, squeals, and reactions to your tone of voice.
- •Many babies at this age can sit with support and hold their head steady, though sitting without support usually comes later.
Milestones to keep in mind
- ✓These are ranges, not a schedule — the next CDC checkpoint is the 6-month checkup, so think of this period as building toward those skills.
- ✓By the 6-month checkup, many babies roll in at least one direction, reach for objects, and babble — some already do, others won't for a few more weeks, and both can be typical.
- ✓Steadier head control and growing interest in sitting are common around now, ahead of the 6-month visit.
- ✓Smiling, laughing, and looking toward familiar faces are well established for many babies by this age.
Growth
💡 Tip for this week
Now that grabbing is in full swing, do a quick reach-zone sweep: keep cords, hot drinks, and small objects out of arm's length, especially during feeds and diaper changes when babies can suddenly roll or lunge.
⚠️ When to call your pediatrician
Call your pediatrician if your baby has fewer than 5-6 wet diapers a day, a fever of 100.4°F (38°C) or higher, isn't gaining weight, rarely makes eye contact or smiles, feels unusually floppy or stiff, or over time shows little interest in reaching for objects or holding the head up. Trust your instincts and ask if anything feels off.
Frequently asked
How much should a 21-week-old (5-month) baby eat?
Most 5-month-olds drink about 24-32 oz of breast milk or formula a day, spread over roughly 4-6 feeds. Milk is still the main source of nutrition at this age, and solids typically wait until closer to 6 months — check with your pediatrician on timing.
What are the wake windows at 21 weeks?
Around 5 months, many babies stay awake about 2 to 2.5 hours between sleeps, usually taking 3 naps and sleeping roughly 14-15 hours total over 24 hours. Every baby is a little different.
Should my baby be rolling over at 21 weeks?
Many babies roll from front to back around this age, and some roll back to front, but there's a wide normal range. By the 6-month checkup, rolling in at least one direction is common. Mention it to your pediatrician if you have concerns — and once rolling starts, always place baby on their back to sleep.
Looking for the bigger picture? See the month 5 overview →
General guidance, not medical advice. Every baby develops at their own pace — talk to your pediatrician with any concerns.