Enter an age — years, and optionally months and days — and the date it applied (today by default). The calculator works backwards to the birth date.
This works backwards from an age to a date of birth. If you only know the age in years, the result is the latest possible birth date — someone could have been born up to a year earlier and still be that age.
Use this free reverse age calculator to find a date of birth from an age. Enter the age — and the date it applied — and it works backwards to the birth date.
A reverse age calculator does the opposite of a normal age calculator: instead of date of birth → age, it takes an age and a reference date and finds the birth date.
birth date = reference date − age (years, months, days) (reference date defaults to today)
So someone who is 30 on 13 June 2025 was born on 13 June 1995; an age of 25 years 6 months on that date gives 13 December 1999.
| Use case | Example |
|---|---|
| Find a birth year | “They’re 45 — what year were they born?” |
| Forms & eligibility | “Must be 18 by 1 Sept — born on or before…” |
| Historical records | “Aged 62 in 1910 census → born ~1848” |
| Quizzes & trivia | Working back from a stated age |
If you only know the age in whole years, the result is the latest possible birth date. The person could have been born any time in the preceding year and still be that age — add months and days for an exact date.