Chronological Age Calculator

Enter a date of birth and get exact age in years, months and days on any date, plus total months, weeks and days.

Dates & TimeWorldwideSource: Gregorian calendar arithmeticFree, no sign-up

Date of birth

Age on (test date or today)

The second date starts at today; change it to a test or assessment date to get age on that day.

Chronological age on October 24, 2026

11 years, 4 months, 9 days

Written 11;4;9 (years;months;days) · 11.36 years

Total months	136 and 9 days
Total weeks	592 and 5 days
Total days	4,149
Born on a	Monday
Next birthday	Tuesday, June 15, 2027 — 234 days away

What this page cannot tell you

Some test manuals give their own rule for borrowing days and months (for example, counting every month as 30 days) and for rounding the days. When scoring a standardised test, follow the manual's rule if it differs. A birthday on 29 February falls on 28 February in common years here.

How to calculate chronological age

Enter the date of birth. Use the date picker or type it.
Enter the age-at date. It starts at today; set it to a test, assessment or event date.
Read the age. Years, months and days, also written as years;months;days, plus totals.

10 situations that need an exact age

Psychological and educational testing

An examiner needs a child's age in years, months and days on the test date to look up the right norms table.

Speech and occupational therapy

A therapist records chronological age at each assessment.

School entry cut-offs

A parent checks whether a child is old enough on the district's cut-off date.

Sports age groups

A coach confirms a player's age on the league's reference date.

Retirement and benefits

Someone works out their exact age on the date a benefit begins.

Visa and passport forms

An applicant fills in age on the date of application.

Medical records

A nurse notes an infant's age in months and days at a check-up.

Birthday trivia

Someone finds the day of the week they were born and their age in days.

Insurance quotes

An applicant confirms age on a policy's start date.

Genealogy

A family historian works out an ancestor's age at a recorded event.

How chronological age is calculated

The page counts the most whole months from the birth date that do not pass the second date, shows them as years and months, then counts the remaining days. When a birth date falls on the 29th, 30th or 31st, a month added to it lands on the last day of a shorter month (31 January + 1 month = 28 February).

Totals: months = years × 12 + months; weeks and days are whole calendar days divided out. Decimal years = days ÷ 365.2425, the average Gregorian year.

Limits: some standardised test manuals give their own borrowing rule, for example treating every month as 30 days, and their own rounding of days to months. Those can differ from this page by a day or two; when scoring a test, follow the manual. A 29 February birthday falls on 28 February in common years here.

Frequently asked questions

What is chronological age?

A person's exact age measured from their date of birth to a given date, usually written in years, months and days.

How do you write chronological age?

Often as years;months;days, for example 8;4;12 for 8 years, 4 months and 12 days.

How do test manuals calculate it?

Many subtract the birth date from the test date column by column, borrowing 12 months for a year and 30 days for a month. Check your manual's rule; the result can differ from the calendar method by a day or two.

What if the person was born on 29 February?

In common years the birthday is taken as 28 February, a widely used convention. Some laws use 1 March instead.

Can I get age on a past or future date?

Yes. Set the second date to any date after the birth date.

How is the next birthday counted?

As whole days from the age-at date to the next anniversary of the birth date.