How old is your baby, exactly?
Enter a birth date for an instant age in years, months, weeks, and days. Nothing is saved except on your own device.
Everything You Need From a Baby Age Calculator
Parents ask "how old is my baby" more than almost any other question in the first three years — for a pediatrician visit, a milestone check-in, or just to answer a curious grandparent. This free age calculator of baby birth dates gives you the answer instantly. Enter a date of birth once, and the baby age calculator above works out the exact age in years, months, weeks, and days, updating live as you type. There's no submit button, no account to create, and nothing you enter is sent to a server — the whole calculation happens right in your browser, so the result appears the moment you finish typing a date.
Age Calculator of Baby in Weeks
In the first few months, most parents and pediatricians count age in weeks rather than months, since a month can run anywhere from 28 to 31 days and doesn't map cleanly onto a newborn's rapid week-by-week changes. This tool works as an age calculator of baby weeks — or, if you prefer the other common phrasing, an age of baby in weeks calculator — showing the total number of complete weeks since birth, worked out with full calendar accuracy, leap years included, so you always get an exact number instead of a rough estimate.
Age Calculator of Baby in Months
Once a baby passes the two-to-three-month mark, most tracking — growth charts, vaccination schedules, everyday conversation — switches from weeks to months. As an age calculator of baby months, this tool converts the same birth date into a precise month count, accounting for the fact that months vary in length. You'll never have to do the mental math of whether 10 weeks is "2 months and a bit" — the answer is calculated exactly and shown right alongside the weeks and days.
Age Calculator of Baby in Days and Years
For the most precise answer — useful for a "100 days old" celebration, a form that asks for age in days, or just curiosity — this age calculator of baby days gives the exact day count too. Once your baby crosses into toddlerhood, the same tool works just as well as a simple age calculator of years, showing whole years alongside the months and days left over. Whether you need a baby age calculator in weeks and months for a newborn, or a straightforward age calculator of years for an older toddler, one date of birth handles all of it at once.
One Date, Every Unit
Unlike calculators that make you pick a mode — weeks, or months, or years — this one shows all four units side by side from a single input, so you get the full picture at a glance no matter how you're used to counting. It works the same way whether you're checking a newborn's age in days for a hospital form or a toddler's age in months for a preschool application. If your baby was born early, the FAQ below explains how corrected age is worked out, so you can adjust the numbers yourself for growth and milestone tracking.
Nothing you enter is stored on a server; a date is only ever remembered in your own browser's local storage, purely so you don't have to re-enter it on your next visit. There's no sign-up, no ads interrupting the result, and no waiting — just an accurate answer to how old your baby is, the moment you type in a date. And once you know the exact age, you can check what it means for your baby's zodiac sign, with a personality and parenting guide for all twelve.
Frequently asked questions
How is my baby's age calculated?
It's the exact time elapsed from the date of birth to today, shown in years, months, weeks, and days.
Why does my baby's age in weeks not match their age in months?
Months vary in length (28–31 days), so a simple “weeks ÷ 4” estimate is inaccurate. A more precise conversion divides total weeks by about 4.345.
Is 12 weeks the same as 3 months?
Not exactly — 12 weeks is closer to 2 months and 3 weeks, since months aren't a fixed number of weeks.
What is corrected (adjusted) age, and when should I use it?
Corrected age subtracts the number of weeks a baby was born premature from their chronological age. It's used for tracking developmental milestones, typically until age 2–3.
How do I calculate my premature baby's adjusted age?
Subtract the number of weeks early from their actual age in weeks. For example, a baby born 4 weeks early who is 10 weeks old has a corrected age of 6 weeks.
Do vaccination schedules use chronological age or corrected age?
Vaccinations follow actual birth date (chronological age), even for premature babies — only developmental milestones use corrected age.
Why do doctors ask for my baby's age in weeks instead of months?
Early developmental screening, feeding guidance, and medication dosing are tied closely to weekly age, especially in the first few months.
When should I switch from counting my baby's age in weeks to months?
Most parents and providers shift to months around 3 months old, and to years around age 2 — though there's no strict rule.
How many days old is my baby?
Total days since birth, counted from date of birth to today.
Can I calculate my baby's age on a future or past date, not just today?
Not currently — this calculator always compares the date of birth to today's date. Support for choosing a different reference date may be added later.
What if I don't know my baby's exact birth time, only the date?
Age is calculated using full calendar days, so exact birth time isn't needed for standard year/month/week/day results.
How accurate is a baby age calculator compared to manual counting?
It accounts for varying month lengths and leap years automatically, which manual estimates often get wrong.