How Old Is My Baby?

How to Calculate Your Baby's Age

Knowing your baby's exact age is more than just a fun fact — it's essential for tracking developmental milestones, scheduling vaccinations, and understanding your child's growth. Our free baby age calculator gives you a precise breakdown of your baby's age in years, months, weeks, days, and even hours from the moment they were born.

Why Exact Age Matters

Pediatricians and child development experts track milestones by specific age ranges. A baby who is "around 4 months" could be anywhere from 14 to 19 weeks old — and the developmental expectations are quite different across that range. Rolling over, for instance, typically begins between 4 and 6 months, but knowing the exact week helps you understand whether your baby is right on track or if it's something to bring up at your next well-baby visit.

During the first year especially, growth happens rapidly. Babies go through predictable growth spurts, developmental leaps (sometimes called "Wonder Weeks"), and sleep regressions. These phases are tied to specific age windows measured in weeks, not rough monthly estimates. That's why our calculator shows both the standard year-month-day breakdown and the total weeks.

Adjusted Age for Premature Babies

If your baby was born before 37 weeks of pregnancy, their pediatrician likely uses an "adjusted age" or "corrected age" to assess development. Adjusted age is calculated from the original due date rather than the actual birth date. For example, a baby born 8 weeks early who is now 6 months old would have an adjusted age of about 4 months. Our calculator handles this automatically — just enter both the birthday and the original due date.

Most doctors use adjusted age for tracking milestones until a child is about 2 to 3 years old, at which point the developmental gap from prematurity has usually closed. It's completely normal for a premature baby to reach milestones later based on their birth date, but right on time based on their adjusted age.

What You Can Track With This Tool

Beyond the basic age calculation, our tool shows your baby's zodiac sign, the day of the week they were born, and a countdown to their next birthday. The milestone timeline gives you a visual overview of key developmental stages from 1 month all the way to 3 years. As your baby grows, you can come back anytime to check their current position and see what's coming next.

All calculations happen instantly in your browser. We don't store any personal information, and no data leaves your device. You can share the results with family and friends using the share button, which creates a simple text summary of your baby's age.

Whether you're a first-time parent wondering what to expect next, a grandparent curious about developmental stages, or just someone who loves numbers — this tool is designed to make tracking your baby's growth easy, accurate, and beautiful.