Child age calculator

How old your child is in years, months and days — precisely, without counting on your fingers. The calculator shows the age today or on any chosen date, converts it into months, weeks and days, and lists the nearest milestones: 100 days, half a year, one year, 1000 days and the next birthday.

Why age in months and days matters

• Paediatrics and norms. Up to age two, almost everything is given in months: growth and weight norms, sleep schedules, check-up timings.
• Development. Skills and milestones are tied to months, not to “about a year” — a couple of months makes a visible difference at this age.
• Forms and sign-ups. Nurseries, clubs and questionnaires often ask for the exact age on a specific date.
• Reasons to celebrate. 100 days and 1000 days are lovely family dates that are easy to miss.

How months are counted

By the calendar, not in 30-day blocks. From 15 March to 15 May is exactly 2 months, even though those months have different day counts. That’s why “total months” and “total days” don’t convert by simply multiplying by 30: a year has 12 months but 365 days, not 360.

FAQ

How many weeks old is my child?

The calculator shows the full number of weeks since birth. In the first months doctors and charts often work in weeks, so it’s a handy reference for newborns.

Can I calculate the age on a past or future date?

Yes — set the day you need in the “Calculate as of” field. It’s useful for filling in a form for an appointment date, or working out how old your child will be by a trip or the start of nursery.

What is a baby’s “100 days”?

Many cultures celebrate a baby’s hundredth day of life. The date lands at roughly 3 months and 8 days — the calculator works it out exactly and shows how long is left.

What if my baby was born prematurely?

This calculator gives the ordinary (chronological) age from the date of birth. To assess a premature baby’s development you need the corrected age — adjusted for the weeks missed before term.