Free calculator
Birth Year Calculator
Estimate a birth year from age, birthday status and a selected reference date.
Find a likely birth year
Use current age and whether the birthday has already occurred.
🔒 Calculations run locally in your browser.
The basic formula
If the birthday has occurred, subtract age from the reference year. If it has not occurred, subtract one additional year. When birthday status is unknown, both possible years are shown.
Privacy
Input values are processed by JavaScript in your browser. The calculator code does not submit them to a server or place them in the URL.
Frequently asked questions
Why can there be two possible birth years?
If you only know someone’s age, the birth year depends on whether their birthday has occurred in the reference year.
Can I use a historical reference date?
Yes. Choose the date on which the stated age was true.
Is the generation label exact?
Generation boundaries are approximate and differ between sources.