Age Calculator
Calculate precise age from a date of birth.
Your inputs
Your inputs and files stay on your device.
Your result
A little input. A useful answer.
Enter your values and run the tool to see your result here.
How to use it
- Enter the date of birth.
- Choose the date on which to calculate age.
- Calculate to see years, months, days and total days.
The method
Dates are compared as calendar dates without time-of-day offsets. Full anniversaries are counted first, followed by calendar months and remaining days.
For example
From 1 January 2000 to 1 January 2025, the age is exactly 25 years.
29 February anniversaries use 1 March in non-leap years. This is a calendar convention, not a jurisdiction-specific legal age rule.
Using Age Calculator with the right inputs
Calculate precise age from a date of birth. Start by matching your task to the quantities and options shown below. The definitions of the inputs matter as much as the final number or transformed output; retain the original values so that you can repeat or check the result.
Inputs and options explained
- Date of birth: select a calendar date. Check the ordering of start and end values and any option controlling whether an endpoint is counted.
- Calculate age on: select a calendar date. Check the ordering of start and end values and any option controlling whether an endpoint is counted.
Example to try in this tool
Use the following sample values to see how the controls and result fit together. They are an illustration of the operation, not recommended values for your own situation.
- Date of birth: 2025-01-01
- Calculate age on: 2026-09-15
Select Calculate age. The result begins with:
Your age
1 years
8 months and 14 days
Total days
622
This example records the tool’s output for those inputs. Check the method and assumptions against your own task before using a result; reproducing an example is not independent certification of the underlying model.
Interpretation and limitations
Define whether your task concerns calendar dates or elapsed time before comparing results. Inclusive endpoints, local time zones, daylight-saving changes and holiday calendars can lead to different answers. A date calculation does not establish a legal or contractual deadline.
Why can two date tools show different totals?
They may include different endpoints or use different calendars, time zones or working-day definitions. Compare those conventions before treating the difference as an arithmetic error.
Before you use the output
- Choose the intended action: Calculate age. Re-run the operation after changing an input or mode so that you are checking the updated result.
- Read the result label and any accompanying explanation. Keep the input values or source file with the output so that a later comparison uses the same assumptions.
- If a result looks unexpected, check units, separators and selected options first. Try a smaller example you can verify rather than repeatedly changing several settings at once.
Questions or a result that needs checking?
If you find a discrepancy, report a problem with Age Calculator. Include a non-sensitive example, the selected options, the result you expected and the result shown. This makes the issue easier to reproduce. See About & privacy for how the site handles tool inputs.