How do I calculate my baby's age in months?

Count the number of complete months from the birth date to today. For example, a baby born on January 15 is exactly 3 months old on April 15. Our calculator does this automatically and also shows weeks and days remaining, so you get a precise reading like "3 months, 1 week, 4 days."

What is corrected age and when do I use it?

Corrected age (also called adjusted age) is used for premature babies. It adjusts for the weeks a baby was born early by subtracting those weeks from their chronological age. For example, a 6-month-old who was born 8 weeks early has a corrected age of about 4 months. Developmental milestones are measured against corrected age until a baby is 2 years old. After age 2, the difference is usually no longer clinically significant.

When do babies typically reach their milestones?

Developmental milestones are ranges, not exact dates. A baby who rolls at 3 months and one who rolls at 5 months can both be developing normally. The milestones listed are based on CDC and AAP guidelines and reflect what most babies can do within a given age range. Always use your baby's corrected age if they were premature, and discuss any concerns with your paediatrician rather than comparing to other babies.

How much should my baby sleep at this age?

Sleep needs vary by age and individual baby. The AAP recommends 14–17 hours for newborns, 12–16 hours for infants (4–11 months), and 11–14 hours for toddlers (1–2 years), including naps. These are total sleep hours across a 24-hour period. If your baby consistently sleeps far less than the recommended range and seems unhappy or unwell, mention it to your paediatrician.

When is my baby's next vaccination due?

Our calculator shows upcoming vaccines based on the CDC recommended immunisation schedule. This is a general guide — your paediatrician's records are the authoritative source. If your baby missed a scheduled vaccine, it can usually be given at the next visit; you do not typically need to restart the series. Always bring your baby's vaccination record to every well-child visit.

My baby isn't hitting a milestone listed for their age. Should I be worried?

Not necessarily. Milestone ranges are broad for good reason — babies develop at different rates. A baby who is not yet doing something listed for their age may simply be at the earlier end of normal. The "red flags" listed for each age are the signs that warrant a conversation with your paediatrician — not the milestone list itself. If you have any concern, trust your instincts and call your doctor; that's always the right call.

Baby Age Calculator

Find your baby's exact age in months, weeks, and days — plus milestones, sleep needs, and vaccination reminders.

Understanding Your Baby's Development

Developmental milestones are ranges, not deadlines. The CDC publishes milestone checklists as guides for what most babies can do by a certain age — but "most" means roughly 75–90%, which means 10–25% of healthy, normally-developing babies haven't reached a milestone at the listed age. That's a wide, normal range.

If your baby was born premature, always use their corrected (adjusted) age when checking milestones. A baby born 8 weeks early who is 5 months old chronologically has a corrected age of about 3 months — and should be measured against 3-month milestones, not 5-month ones. This correction is used until age 2.

The best developmental investment you can make at any age is talking, reading aloud, and responding to your baby's cues. Research consistently shows that the quantity and quality of words spoken to a baby in the first 3 years has a stronger impact on language development than any toy, app, or programme.

Baby Age Calculator — Frequently Asked Questions

Sources & Methodology

Last reviewed: October 17, 2026

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Understanding Your Baby's Development

Baby Age Calculator — Frequently Asked Questions

Sources & Methodology

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