How Old Is My Baby?

How to Calculate Your Baby's Age

Your baby's exact age is not just trivia; it underpins tracking developmental milestones, scheduling vaccinations, and understanding your child's growth. The free baby age calculator gives you a precise breakdown in years, months, weeks, days, and 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 adjusted age 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. You can also convert weeks to months or check how old your baby will be on any future date.

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.

First-time parent, grandparent, or just curious about the numbers: the calculator makes tracking your baby's growth quick and precise, with no signup and nothing to install.

More Than a Calculator

My Baby Wonder is also a growing set of free baby tools and games, from due date and sleep calculators to gentle sensory games like Baby Smash, plus a curated guide to screen-free educational toys for ages 0 to 5. The toy picks are organized into practical lists such as Montessori at Home and Screen-Free Travel Kit, each independently selected with an honest take on what is worth buying.