Formula and calculation method
Completed years = reference year − birth year, subtracting one before the birthday. Total days = date difference.
UTC calendar dates. Leap-day birthdays use March 1 in non-leap years for completed years.
How to use age calculator
- Set Birth date. The example below uses 1995-04-15.
- Set Age on date. The example below uses 2026-10-06.
- Select Calculate to update the result. Reset restores the illustrated inputs. Copy, print or download your own result if you need a record.
Worked example
Example inputs
- Birth date
- 1995-04-15
- Age on date
- 2026-10-06
- Completed years
- 31
- Total days
- 11497
Factors affecting your result
UTC calendar dates. Leap-day birthdays use March 1 in non-leap years for completed years.
Changing birth date changes the scenario being evaluated. Adjust one input at a time when comparing results, keep a copy of the assumptions, and compare values using the same unit and period. A precise arithmetic result does not make an uncertain assumption precise.
Frequently asked questions
How does the age calculator work?
Completed years = reference year − birth year, subtracting one before the birthday. Total days = date difference.
What inputs does Age Calculator need?
Enter birth date, age on date. Choose values that correspond to the same situation and measurement convention.
How should I interpret the age calculator result?
UTC calendar dates. Leap-day birthdays use March 1 in non-leap years for completed years.
Are my age calculator inputs uploaded?
No. The calculation runs in this browser. Favorites, recent tool names, theme and formatting preferences may be saved locally, but calculation inputs are not sent to a calculation server or stored by this website. Shared links do not include entered values.
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