Chronological Age Calculator

Calculate chronological age in years, months and days for test scoring, with the calendar or 30-day-month method.

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How to use this calculator

Enter your values. The result updates as you type; press Calculate to confirm and jump to the result on mobile. Use Share to send the calculator with your result.

How chronological age is calculated

Write the test date and the birth date as year, month and day, then subtract from right to left. If the days are negative, borrow one month (as 30 days in the test-manual method, or the actual days in the previous month in the calendar method); if the months are negative, borrow one year (12 months).

2026 ; 10 ; 05 test date − 2018 ; 03 ; 21 birth date = 8 ; 6 ; 14 (borrowing 30 days)

Frequently asked questions

Do I round up the days?

Some tests round 16+ days up to a full month, others don’t. Check the manual.

About this tool

Written by
[Author: to be assigned]
Reviewed by
Formula tests passed · human review pending
Last updated
31 Oct 2026

See our methodology and editorial policy. Think something’s off? Report an error with this tool.

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