⚰️ Age at Death Calculator
Enter a birth date and death date to calculate the exact age at death — useful for verifying genealogical records and family history research.
How the age at death is worked out
Both dates are read as UTC midnight, so no time zone can shift one by a day. The year, month and day parts are then subtracted separately, borrowing where a part goes negative:
years = deathYear - birthYear, months = deathMonth - birthMonth,
days = deathDay - birthDay
if days < 0 : days += length of the month before the death month; months -= 1
if months < 0 : months += 12; years -= 1
total days lived = (death - birth) / 86,400,000 msTake a man born 30 November 1842 who died 14 March 1911. The raw parts are 69 years, −8 months, −16 days. February 1911 had 28 days, so the day borrow gives 12 days and drops the months to −9, which borrows again to 3 months and 68 years: 68 years, 3 months, 12 days, and 24,940 total days lived.
Entering the dates
- Both fields are required, and the death date must fall on or after the birth date; reversing them returns an error rather than a negative age.
- The total-days count is exact, leap days included. That is the figure worth quoting when you check a headstone against a burial register.
- Same-day birth and death gives 0 years, 0 months, 0 days, the correct entry for an infant who did not survive the day.
Frequently asked questions
How old was someone born on 28 February 1900 who died on 4 July 1975?
75 years, 4 months and 6 days, or 27,519 days. The day part borrows the 30 days of June 1975 to settle the gap from the 28th to the 4th.
Does the calculator count leap days?
Yes. The total-days figure is the true difference between the dates, so every 29 February between them counts. Remember that 1900 was not a leap year and 2000 was.
What if I only know the year of birth?
Use a stand-in day such as 1 July and treat the answer as approximate. It can be a full year out either way, so record it as "about 68" in your tree.