How to use the age calculator
- Date of birth: Select the actual birth date.
- Age on date: Select the date on which to measure age.
- Select Calculate to see the result. Change any input and calculate again to compare.
Worked example
January 1, 2000 to January 1, 2026 is 26 years.
Formula and assumptions
Birth date → calendar difference → age.
Calendar months are counted using a last-day-of-month anniversary when a date does not exist. This is not a legal-age determination.
Common questions
Why might my result differ from another estimate?
Calendar months are counted using a last-day-of-month anniversary when a date does not exist. This is not a legal-age determination. Keep the same inputs and rounding when comparing tools.
Are my entries saved?
No. Calculations run on your device. Reloading or closing this page may clear your entries.