CALCULATORS · FREE

Baby age calculator

Find out how old your baby is in months, weeks and days, and switch on corrected age if your baby was born early.

Enter your baby’s date of birth to see their age.

How to use the baby age calculator

  1. Enter your baby’s date of birth.
  2. Leave “Age on” as today, or pick another date to see how old your baby was or will be.
  3. If your baby was born early, switch on “Born early?” and enter the weeks born early or the due date to see the corrected age.

How the age is worked out

The calculator counts complete years, months and days from the date of birth to the “Age on” date using the calendar, so months of different length and leap years are handled. If the birth day does not exist in a later month (for example the 31st, or 29 February), the last day of that month is used. Total months, total weeks and total days are shown as well.

Corrected age moves the starting date forward by the number of weeks your baby was born early, so it shows how old your baby would be if they had been born on the due date.

Frequently asked questions

What is corrected age?

Corrected age (also called adjusted age) is your baby’s age counted from the due date instead of the birth date. For example, a baby born 8 weeks early who is 6 months old has a corrected age of about 4 months. It is commonly used for premature babies until around age 2. Ask your paediatrician how to use it for your baby.

How many weeks are in a month?

A month is about 4.3 weeks on average (52 weeks divided by 12 months). Calendar months have 28 to 31 days, so the exact number of weeks changes from month to month. That is why this calculator also shows total weeks and total days.

How do I count my baby’s age in months?

Count complete calendar months from the date of birth. A baby born on the 15th is one month old on the 15th of the next month. If that day does not exist in the month (for example the 31st), the last day of the month is used. The calculator does this for you.

Should I use chronological age or corrected age?

Both are shown when you switch on “Born early?”. Corrected age is commonly used for premature babies until about age 2, and your paediatrician or health visitor will tell you which one to use for your baby.

Does this replace medical advice?

No. It is a date calculator for general information. For questions about your baby’s growth, feeding or development, speak to a paediatrician, your doctor or a health visitor.

For general information only, not medical advice.

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