Age Calculator: Calculate Age from Date of Birth in Excel

Calculate Age from Date of Birth

Enter the date of birth and, optionally, an “as of” date to calculate the age in years, months, and days, similar to how you might calculate age using date of birth in Excel.

What is Calculating Age from Date of Birth in Excel?

Calculating age from a date of birth in Excel involves determining the duration between a person’s birth date and a specified date (usually today or another specific “as of” date), expressed in years, months, and days. Excel provides several methods to calculate age using date of birth in Excel, most notably using the `DATEDIF` function, which is designed for calculating the difference between two dates in various intervals. You can also perform manual calculations using date functions like `YEAR`, `MONTH`, and `DAY`, although `DATEDIF` is generally more straightforward for this specific task.

Anyone who needs to find the age of individuals based on their birth dates stored in an Excel sheet would use this. This includes HR professionals, school administrators, event organizers, demographers, and anyone managing databases with birth dates. A common misconception is that simply subtracting the birth year from the current year gives the correct age; this is often incorrect as it doesn’t account for the month and day within the year.

Calculate Age Using Date of Birth in Excel: Formula and Explanation

The most common and efficient way to calculate age using date of birth in Excel is with the `DATEDIF` function. The `DATEDIF` function calculates the difference between two dates based on the interval specified.

The syntax is: DATEDIF(start_date, end_date, unit)

• start_date: The date of birth (e.g., cell A1 containing “1990-05-15”).
• end_date: The date as of which you want to calculate the age (e.g., `TODAY()` for the current date, or another cell like B1 containing “2024-01-20”).
• unit: The type of interval you want to return:
  • "Y": Complete years between the two dates.
  • "M": Complete months between the two dates.
  • "D": Complete days between the two dates.
  • "YM": Complete months after subtracting the complete years.
  • "MD": Complete days after subtracting complete years and months.
  • "YD": Complete days after subtracting complete years (ignoring months).

To get the age in Years, Months, and Days, you would use `DATEDIF` three times:

• Years: =DATEDIF(A1, TODAY(), "Y")
• Months: =DATEDIF(A1, TODAY(), "YM")
• Days: =DATEDIF(A1, TODAY(), "MD")

You can combine these into one cell: =DATEDIF(A1, TODAY(), "Y") & " Years, " & DATEDIF(A1, TODAY(), "YM") & " Months, " & DATEDIF(A1, TODAY(), "MD") & " Days"

Variables Table

Variable	Meaning	Unit/Type	Typical Value
start_date	The beginning date (Date of Birth)	Date	e.g., “1990-05-15”
end_date	The ending date (As of date, often TODAY())	Date	e.g., `TODAY()` or “2024-01-20”
unit	The interval to calculate	Text (“Y”, “M”, “D”, “YM”, “MD”, “YD”)	“Y”, “YM”, “MD” for full age

Table explaining the DATEDIF variables used to calculate age using date of birth in Excel.

Practical Examples (Real-World Use Cases)

Example 1: Calculating Age for an Employee

An HR department needs to find the current age of an employee born on June 25, 1985, as of January 20, 2024.

• Start Date (Date of Birth): 1985-06-25
• End Date (As of Date): 2024-01-20

Using Excel `DATEDIF`:

• Years: DATEDIF("1985-06-25", "2024-01-20", "Y") = 38
• Months: DATEDIF("1985-06-25", "2024-01-20", "YM") = 6
• Days: DATEDIF("1985-06-25", "2024-01-20", "MD") = 26 (25th June to 20th July is 25 days, but it is 20th Jan)
  It should be from June 25 to Jan 20…
  From June 25, 1985 to June 25, 2023 is 38 years.
  From June 25, 2023 to Jan 25, 2024 is 7 months. But it’s Jan 20, so 6 full months (June 25 to Dec 25).
  From Dec 25, 2023 to Jan 20, 2024: Dec has 31 days, so 31-25=6 days in Dec + 20 days in Jan = 26 days.
  So, 38 Years, 6 Months, 26 Days.

Result: The employee is 38 years, 6 months, and 26 days old.

Example 2: Calculating Age of a Student

A school needs to determine the age of a student born on September 1, 2010, as of September 1, 2023.

• Start Date: 2010-09-01
• End Date: 2023-09-01

Using Excel `DATEDIF`:

• Years: DATEDIF("2010-09-01", "2023-09-01", "Y") = 13
• Months: DATEDIF("2010-09-01", "2023-09-01", "YM") = 0
• Days: DATEDIF("2010-09-01", "2023-09-01", "MD") = 0

Result: The student is exactly 13 years, 0 months, and 0 days old.

How to Use This Age Calculator

1. Enter Date of Birth: Input the day, select the month, and enter the year of birth in the “Date of Birth” fields.
2. Enter As of Date (Optional): If you want to calculate the age as of a specific date other than today, enter the day, month, and year in the “As of Date” fields. If you leave these blank, the calculator will use today’s date.
3. Calculate: Click the “Calculate Age” button.
4. View Results: The calculator will display the age in years, months, and days, along with total days, approximate total months, and decimal years. The formula explanation shows how you might calculate age using date of birth in Excel using `DATEDIF`.
5. Reset: Click “Reset” to clear the fields and results.
6. Copy Results: Click “Copy Results” to copy the age details to your clipboard.

The results help you understand the exact age between two dates, just as you would find using the excel age formula.

Key Factors That Affect Age Calculation

• Date of Birth: The starting point for the age calculation. An incorrect date of birth will lead to an incorrect age.
• As of Date: The end date for the calculation. Age changes daily, so the ‘as of’ date is crucial. If not specified, it’s usually the current date.
• Leap Years: The `DATEDIF` function and correct date handling automatically account for leap years (February 29th), ensuring accurate day counts over longer periods. Manual calculations must carefully consider leap years to be accurate when calculating total days.
• Month Lengths: Different months have different numbers of days (28, 29, 30, or 31). The “MD” unit in `DATEDIF` correctly handles the varying month lengths when calculating the remaining days after full months.
• Time Component: Excel dates can include time. If times are involved and not just dates, age calculation to the day might be affected if one date is at the beginning of the day and the other at the end. For age in years, months, and days, usually only the date part is considered.
• Excel Date System: Excel stores dates as serial numbers (number of days since January 1, 1900 or 1904). Understanding this helps when troubleshooting date issues but `DATEDIF` handles this internally.

Frequently Asked Questions (FAQ)

1. How do I calculate age in Excel if I only have the year of birth?

You can only calculate an approximate age by subtracting the birth year from the current year: `=YEAR(TODAY()) – BirthYear`. This doesn’t account for month and day.

2. What is the `DATEDIF` function and why is it used to calculate age using date of birth in Excel?

DATEDIF is a built-in Excel function specifically designed to calculate the difference between two dates in years, months, or days. It’s the most accurate and convenient way to calculate age using date of birth in Excel.

3. Is `DATEDIF` available in all versions of Excel?

Yes, but it’s often undocumented in newer versions’ help files, though it still works. It was included for Lotus 1-2-3 compatibility.

4. Can I calculate age in fractional years in Excel?

Yes, you can use the `YEARFRAC` function: `=YEARFRAC(start_date, end_date, [basis])`. This gives the age as a decimal number representing years.

5. How do I handle errors with the DATEDIF function?

The `DATEDIF` function returns a `#NUM!` error if the start_date is later than the end_date. You can wrap it in an `IFERROR` function to handle such cases, e.g., `=IFERROR(DATEDIF(A1, B1, “Y”), “Start date is after end date”)`.

6. Can I calculate the number of days between two dates in Excel without DATEDIF?

Yes, you can simply subtract the earlier date from the later date (e.g., `=B1 – A1`), as Excel stores dates as serial numbers. The result will be the number of days.

7. How do I get today’s date in Excel for age calculation?

Use the `TODAY()` function. For example, `=DATEDIF(A1, TODAY(), “Y”)` calculates years between the date in A1 and today.

8. Why might my manual age calculation be different from DATEDIF?

Manual calculations often oversimplify by assuming average month lengths or not perfectly handling the day-of-month across year/month boundaries, especially compared to `DATEDIF`’s “YM” and “MD” units.

Related Tools and Internal Resources

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