Baby age, week by week
15 Weeks Old — How Many Months?
A 15-week-old baby is 105 days old — about 3 months and 14 days.
This week
Just past 100 days for most babies - a big deal in many cultures. Expect squeals and giggles.
The math
15 weeks = 105 days ≈ 3 months + 14 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 15
At 15 weeks your baby is near the 3 Months mark. Around this age, many babies:
- Lifts their head and chest when lying on their tummy
- Watches faces closely and follows moving things
- Smiles at people all on their own