Calculate Age

Age isn't just a number; it's important information that's used everywhere, from filling out forms to determining eligibility for everything from school enrollment to retirement benefits. Here's how to accurately calculate age, whether you're doing it manually or with tools.

1. Basic Formula

+ Basically, age is the difference between a person's birth date and today's date.

Formula:

Age = Current Year - Birth Year

But this only gives you a rough estimate. To know the exact age (years, months, days), you need to account for the actual month and day.

2. Manual Method (Exact Age)

Suppose a person was born on May 10, 1990, and today is July 21, 2025.

Difference in years: 2025-1990 = 35

Has the birthday passed this year? Yes (May 10 is before July 21), so:

Age is 35

If today were April 5, 2025, then:

May 10 is not yet.

Age is 34, not yet 35

Tip:

If (current month, day) is before birth month, day, subtract 1 from the year difference.

3. Use a calculator or app

Most date calculators or spreadsheet tools like Excel or Google Sheets can accurately calculate age.

In Excel

If cell A1 contains the date of birth:

=DATEDIF(A1, TODAY(), "Y")

This returns the age in whole years.

4. Common Use Cases

ID verification (for example, 18+ for voting, 21+ for alcohol)

Age-based eligibility for school or sports leagues

Pension and retirement planning

Medical calculations