Baby age, week by week
4 Weeks Old — How Many Months?
A 4-week-old baby is 28 days old — not a full month yet.
This week
One month done! Your baby may follow your face for a moment during tummy time.
The math
4 weeks = 28 days ≈ 28 days
A month is longer than 4 weeks — on average 30.44 days — so you can't just divide by 4. The exact answer shifts a little with the calendar, so for the day-perfect number, use the calculator with your baby's real birthday.
Get the exact age →What babies do around week 4
At 4 weeks your baby is near the 1 Month mark. Around this age, many babies:
- Lifts their head for a moment during tummy time (always stay close)
- Knows your voice and likes it more than any other
- Their first real smile may show up between 4 and 8 weeks