How to use the age calculator
Enter the date of birth, then choose the date on which you want to know the age. Today is selected by default, but a past or future comparison date works just as well. This makes the tool useful for both “how old am I?” and age-at-event questions.
Completed years are more than year subtraction
Someone born on 20 October 1990 has not turned 36 on 1 January 2026, even though 2026 minus 1990 equals 36. The birthday must be reached first. The calculator therefore checks the month and day before counting a completed year.
Age in months follows completed calendar months. Weeks and days instead use the exact number of full days between the dates. These totals are alternative views of the same period and should not be added together.
Leap years and 29 February
Leap days are automatically included in the total number of days. For a person born on 29 February, this calculator uses 28 February as the birthday in a non-leap year. That is the tool's consistent calculation rule; a legal or contractual age threshold may apply a different convention.
When to verify the answer
This is a practical date tool, not a legal determination. Check the responsible authority's rules when an exact age threshold affects eligibility, pensions, insurance, or a contract. Dates are calculated without times of day, so every difference represents complete calendar days.