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- Enter the date of death and the age written on the record.
- Choose years, months and days, or years only if that is all the record gives.
- The calculator takes the age away from the death date and shows the birth date.
- With a years-only age, it shows the earliest and latest possible birth dates.
How to use the birth date from age at death calculator
Enter the date of death
Type or pick the death date from the gravestone, death certificate, burial register or obituary.
Pick how the age is given
Choose Years, months, days when the record says something like 72 years, 5 months, 10 days. Choose Years only when it just says age 72.
Type the age
Enter the years, and the months and days if you have them. Use zero for any part that is missing.
Read the result
The headline shows the estimated birth date. The steps below it show each subtraction so you can check the work.
How the birth date is calculated
Genealogists work backwards from the death date. The usual method takes off the years and months first, and then the days. The calculator follows the same order, so the answer matches what you would get by hand.
Birth date formula
Step 1: Date of death minus the years and months
Step 2: Result minus the days
Birth date = date of death − years − months − days
If the day does not exist in the earlier month, the last day of that month is used. For example, March 31 minus one month gives February 28 in a common year.
Worked examples
Example 1: age with years, months and days
A person died on March 15, 1923, aged 72 years, 5 months and 10 days.
- Date of death March 15, 1923
- Minus 72 years and 5 months October 15, 1850
- Minus 10 days October 5, 1850
- Estimated birth date Saturday, October 5, 1850
The estimated birth date is October 5, 1850.
Example 2: age in whole years only
A gravestone says the person died on March 15, 1923, aged 72.
- Latest possible birth date March 15, 1851
- Earliest possible birth date March 16, 1850
- Likely birth year 1850 or 1851
A whole-year age leaves a window of about one year, because the person could have been born on any day in it.
Example 3: a date that does not exist
A person died on February 29, 2000, aged 10 years.
- Date of death February 29, 2000
- Minus 10 years February 28, 1990 (1990 is not a leap year)
The calculator uses the last day of the month when the exact day is missing.
Where a birth date from age at death calculator helps
Gravestones and cemetery records
Many headstones give only the death date and age. This turns them into a birth date to search for.
Census and burial registers
Some records list the age at death or burial. Use it to guess the birth year before searching baptism records.
Obituaries and death certificates
These often print the age in years, and sometimes months and days, which gives a close estimate.
Family trees
Add an estimated birth date to a tree, and note that it is calculated so you can replace it later.
Ages on old records are often rounded, guessed or wrong. Use the calculated date to start your search, then confirm it with a birth, baptism or christening record. Before 1752, Britain and its colonies used the Julian calendar, so dates in those records may need adjusting.
You can also try the age calculator, the date difference calculator and the day of week calculator.
Birth date from age at death calculator FAQ
How do I calculate a birth date from age at death?
Start with the date of death. Subtract the years and months of the age, and then subtract the days. The result is the estimated birth date.
What if the record gives only the age in years?
Then the birth date can fall anywhere in a window of about one year. The calculator shows the earliest and latest possible dates and the likely birth year.
Why is the calculated date not exact?
Old records often round ages or contain mistakes, and the person giving the age may not have known the birth date. The result is a good starting point, not proof.
Does the order of subtraction matter?
It can change the answer by a day or two near the end of a month. The calculator takes off years and months first, and then days, which is the common method.
What happens when the day does not exist in the earlier month?
The last day of that month is used. For example, March 31 minus one month is February 28 in a common year.
Can I use it for living people?
Yes. Enter any date and age, and it works the same way. For the age of a living person, use the age calculator instead.