Find a birth date from an age. This free reverse age calculator works backwards from an age — years, months and days — as of any date to the date of birth, with the birth year and day of week.
The age
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.
Birth date
—
Enter an age
Day of week
—
Birth year
—
As of date
—
Total days lived
—
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.
What this reverse age calculator does
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.
How it works
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.
When it’s useful
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
A note on precision
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.
How to use the reverse age calculator
Enter the age in years (plus months/days if known).
Set the “age as of” date or leave it as today.
Read the birth date, year and day of week.
Reverse Age FAQ
How do I find a birth date from an age?
Subtract the age from the reference date. Someone who is 30 on 13 June 2025 was born on 13 June 1995.
What year was I born if I'm a certain age?
Subtract your age from the current year — but if your birthday hasn't happened yet this year, it's one more. The calculator handles this from the date you enter.
Can I include months and days?
Yes. Add months and days for an exact birth date; with whole years only, you get the latest possible birth date.
Can I use a past or future reference date?
Yes. Set "age as of" to any date — useful for records, eligibility cut-offs and historical calculations.
How is this different from an age calculator?
An age calculator goes from birth date to age; this reverse age calculator goes from age back to the birth date.
Is the reverse age calculator free?
Yes, this reverse age calculator is completely free, needs no sign-up, and gives instant results in your browser.
