Birth date from age at death.

Worked example

Someone died on 15 June 1890 aged 72. If only the years are known, they had completed 72 birthdays but not yet reached 73, so they were born between 16 June 1817 and 15 June 1818. If the stone reads 72 years 3 months 5 days, count back 72 years from 15 June 1890 to 15 June 1818, then 3 months to 15 March 1818, then 5 days to 10 March 1818, a single date.

How it works

The tool counts back from the date of death by the years, then the months, then the days. With days given the answer is one date. With months but no days, it is the window of one month. With years only it is the window of one year, from the day after the date (age + 1) years before death to the date exactly the age in years before death. If counting back lands on a day that does not exist, for example 31 March minus one month, the last day of that month is used.

Dates are treated as Gregorian-calendar dates. For records made under the Julian calendar, convert the dates first with the Old Style New Style Date Converter. This tool uses calendar arithmetic only and cites no outside figures.

Sources and basis (opened 2026-10-08): calendar arithmetic only; no external data or published figures are used.

FAQ

How do I find a birth date from the age at death?

Count back from the date of death by the age. With only years the result is a one-year window; adding months narrows it to a month, and adding days gives one date.

Why do I get a range instead of one date?

An age in whole years only says the person had completed that many birthdays. Their birthday could be any day in the year before the death date, so the range covers every possibility.

What if the record only gives the year of death?

Run the tool once with 1 January and once with 31 December of that year, then combine the two windows to get the earliest and latest possible birth dates.

Does this handle Old Style Julian dates?

No. Dates are treated as Gregorian-calendar dates. For records dated before Britain changed calendars in 1752, convert them with the Old Style New Style Date Converter first.

Why might the calculated date not match a baptism or birth record?

Ages on stones and certificates can be rounded or wrong, and baptism dates follow birth by days or years. Use the result as a window to search for records.