Baby age, week by week
40 Weeks Old — How Many Months?
A 40-week-old baby is 280 days old — about 9 months and 6 days.
This week
Simple words are understood now, and the drop-it-watch-you-fetch-it game begins.
The math
40 weeks = 280 days ≈ 9 months + 6 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 40
At 40 weeks your baby is near the 9 Months mark. Around this age, many babies:
- Stands while holding furniture, steady and proud
- Understands 'no' and other simple things you say
- May cling tight to their favorite people