To find the year someone was born, subtract their age from the current year — then subtract one more if they have not had their birthday yet this year. Someone who is 36 in 2026 was born in 1990 if their birthday has passed, or in 1989 if it is still to come.
The calculator gives the birth year and the full range of possible birth dates. Add the months and days of an exact age and it gives the exact date of birth.
Worked example
Age in years: 36 yearsBirthday this year?: Not sureAge on: October 30, 2026
Born in: 1989 or 1990
Anyone who is 36 on October 30, 2026 was born between October 31, 1989 and October 30, 1990 — in 1990 if they have had their birthday this year, in 1989 if not.
Open this example in the calculator →How to use the Birth Year Calculator
- Enter the age in whole years.
- Say whether the birthday has already happened this year, or leave "Not sure" to get both possible years.
- For an exact date of birth, add the extra months and days of the age.
- Leave "Age on" as today, or set the date the age was given — on a document, for example.
The birth year formula
Birth year = current year − age, if the birthday has already happened this year. If not, subtract one more. In 2026:
- Age 36, birthday already passed: 2026 − 36 = 1990.
- Age 36, birthday still to come: 2026 − 36 − 1 = 1989.
If you do not know, the answer is "one of the two", and the range of possible birth dates is a single year long: anyone aged 36 on October 30, 2026 was born between October 31, 1989 and October 30, 1990.
From an exact age to a date of birth
If you know an age in years, months and days — from a medical record, a school report or a chronological age — you can count back to the exact birth date. 8 years, 4 months and 12 days before October 30, 2026 is June 18, 2018. The calculator does this by counting back the years, then the months, then the days, and checks the answer forward again so the age it gives is exactly the one you entered.
Why age alone cannot give an exact date
An age in whole years covers 365 or 366 possible birth dates — everyone from those turning that age today to those about to turn the next one tomorrow. Adding the months narrows it to about 30 days, and adding the days narrows it to one.
Frequently asked questions
What year was I born if I am 36?
In 2026, 1990 if you have had your birthday this year, or 1989 if it is still to come. In general, subtract your age from the current year, and subtract one more if your birthday has not happened yet.
How do I calculate my birth year from my age?
Current year minus age. If the birthday is still to come this year, subtract one more.
Can I find an exact date of birth from an age?
Yes, if you know the age in years, months and days on a particular date. Enter all three and the date, and the calculator gives the exact birth date.
What year was someone born who is 18 today?
In 2026, they were born in 2008 if their 18th birthday has passed this year, or 2007 if it has not.