How to use the Chronological Age Calculator
- Enter the date of birth.
- Enter the date of testing. It starts as today.
- Read the age in years, months and days, and the years;months format (for example 7;4).
What is chronological age?
Chronological age is the exact time someone has been alive, measured from their date of birth. Teachers, school psychologists, speech therapists and doctors use it to look up the right norms for a test, because scores on many assessments are compared with people of the same age, down to the month.
How it's calculated
Subtract the date of birth from the test date: first whole years, then whole months, then the remaining days. A child born on 20 June 2018 and tested on 2 November 2025 is 7 years, 4 months and 13 days old, written 7;4.
Doing this by hand means borrowing days and months, which is easy to get wrong. The calculator handles months of different lengths and leap years for you.
Rounding
Most tests use the age in completed years and months, with the days dropped. Some test manuals tell you to round up to the next month when the days are 15 or more, or never to round. Always follow the manual for the test you're scoring.
Frequently asked questions
What does 7;4 mean?
7 years and 4 months. The semicolon separates years from months, so it isn't confused with a decimal like 7.4.
Can I calculate age on a past or future date?
Yes. Change the date of testing to any date.
Is the information stored?
No. Dates are calculated in your browser and never saved or sent.