The Age Calculator tool is a computer program or an online application that calculates the age of an individual based on their date of birth and the current date. It is a simple yet useful tool that can quickly determine a person's age in years, months, days, hours, minutes, and even seconds.

To use the Age Calculator tool, a user needs to input their date of birth in the specified format, which is usually the month, day, and year. The tool then uses the current date and time to calculate the age of the user. The result is typically displayed in an easily understandable format, such as "You are 25 years, 3 months, and 15 days old."

The Age Calculator tool can be used for various purposes, such as to calculate the age of a person for legal or medical reasons, to determine eligibility for certain programs, or simply to satisfy one's curiosity about their age. Many online versions of the tool also provide additional features, such as the ability to calculate the age of a group of people or to compare the age of two individuals.