Birth Year Calculator
Find the year someone was born from their current age — with both possible years shown when you are not sure whether their birthday has passed.
Result
Someone tells you their age and you want to know what year they were born — this birth year calculator answers instantly. Enter the age, say whether their birthday has already happened this year, and it returns the birth year. If you pick "not sure", it shows both possible years with the reasoning for each, because an age alone always leaves two candidates.
The math is simple but easy to get wrong by one. If the birthday has already passed this year, the birth year is the current year minus the age. If it is still ahead, the person will only turn their next age later this year, so you subtract one more: current year minus age minus one. That off-by-one is exactly why forms and quizzes that ask only for an age can never pin the birth year down to a single value.
The calculator reads the current year from your device's clock at the moment you press the button, so it never relies on a year baked in when the page was built — the same page keeps giving correct answers next January without any update. It works for filling in forms, verifying ages on documents, figuring out a colleague's graduation cohort, or settling a birthday-party debate.
If you have the full date of birth and want the reverse — the exact age in years, months and days, plus a countdown to the next birthday — use our Age Calculator instead; it is the companion tool to this one. Both run entirely in your browser, and nothing you enter is sent anywhere.