Baby Age Calculator
Enter your baby's date of birth to get their precise age in weeks, months, days, and hours, along with their current developmental stage and zodiac sign. Free, instant, and private, nothing leaves your device.
This calculates adjusted age for milestone tracking.
Why an exact age, not a rounded one
Pediatricians track milestones, vaccines, and feeding by precise age windows. "Around four months" can mean anywhere from 14 to 19 weeks, and the developmental expectations differ across that span. This calculator gives you the exact week and day so you always know where your baby actually stands.
Weeks, months, or both
In the early months, weeks are the natural unit, development moves fast enough that a 4-week-old and a 6-week-old are meaningfully different. Around 3 to 4 months, months become more practical. The calculator shows both at once so you never have to convert in your head. To go the other way, the weeks to months converter handles any weeks-and-days combination.
Premature babies
If your baby arrived before 37 weeks, milestones are usually tracked by adjusted age, calculated from the original due date. The adjusted age calculator does this automatically. Most doctors use adjusted age until a child is about 2 to 3 years old.
What else you can track
Alongside exact age, you can see your baby's developmental leap window, browse milestones by age, and find stage-matched, screen-free toy picks for what comes next.
Frequently Asked Questions
How does the baby age calculator work?
Enter your baby's date of birth. The calculator instantly returns their exact age in years, months, weeks, days, and hours, plus total days and weeks since birth. Everything runs in your browser, nothing is stored or sent anywhere.
How do I calculate my baby's age in weeks and months?
Pick the birth date and the calculator shows both at once: the full year-month-day breakdown and the running total in weeks. Weeks and months do not divide evenly (a month averages about 4.35 weeks), so the tool does the precise math for you.
Can it calculate adjusted age for a premature baby?
Yes. For preemies, use the adjusted age calculator, which counts from the original due date rather than the birth date. Pediatricians use adjusted age to track milestones until about 2 to 3 years old.
Is the baby age calculator free?
Yes, completely free with no sign-up. There are no limits and no account required.