Chronological Age Calculator
Calculate exact chronological age from a date of birth — enter the birth date and an optional “as of” date to get the age in years, months and days.
How to calculate chronological age
Chronological age is the exact amount of time someone has been alive — the span from their date of birth to a reference date, usually today. You subtract the birth date from the reference date and express the result in years, months and days, carrying months and accounting for leap years. Enter the date of birth above (and a test date if it isn’t today) and the calculator returns the exact age, plus the total in days and months.
For example, someone born on June 15, 2015 is, on March 1, 2026, 10 years, 8 months and 14 days old. Because months have different lengths, the calculator borrows the right number of days when the day-of-month subtraction goes negative.
Why exact chronological age matters
Many standardized tests and developmental assessments — in education, speech-language therapy and psychology — score a person against others of the same exact age, so the age must be precise to the day. That is why scoring forms ask for the test date and the date of birth and expect an age in years, months and days rather than a rounded number.
Chronological age is your actual age (time since birth), as opposed to “biological age,” a health-based estimate. To add or subtract days from a date instead, use the deadline calculator.
Frequently asked questions
How do you calculate chronological age?
Chronological age is the time elapsed from the date of birth to a reference date (usually today). You subtract the birth date from the current date and express the result in years, months and days. The calculator does the date arithmetic, including leap years, for you.
Is chronological age your actual age?
Yes — chronological age is simply how long you have been alive, measured from your birth date. It differs from “biological age” (a health-based estimate) or “developmental age” (skills-based). Clinicians and educators use exact chronological age in years, months and days for test scoring.
Why is chronological age used in testing?
Many standardized assessments compare a person’s score to others of the same exact age, so the age must be precise to the day. Entering the test date and the date of birth gives the chronological age that maps to the correct norm table.