Calculate Age In Excel Using Date Of Birth

Calculate Age

Excel DATEDIF Function Units

Unit Argument	Meaning	Description
“y”	Years	Completed number of years between the dates.
“m”	Months	Completed number of months between the dates.
“d”	Days	Total number of days between the dates.
“ym”	Months excluding years	Completed number of months, ignoring years.
“md”	Days excluding years and months	Completed number of days, ignoring years and months.
“yd”	Days excluding years	Completed number of days, ignoring years (as if dates were in the same year).

Understanding the ‘unit’ argument in Excel’s DATEDIF function is key to calculate age in Excel using date of birth correctly.

What is Calculate Age in Excel Using Date of Birth?

To calculate age in Excel using date of birth, you typically use the `DATEDIF` function. This powerful function is designed to find the difference between two dates in various units like years, months, or days. It’s particularly useful for calculating the exact age of a person or the duration between two events as of a specific date.

The `DATEDIF` function takes three arguments: a start date, an end date, and a unit. For age calculation, the start date is the date of birth, and the end date is usually today’s date or another specific date up to which you want to calculate the age. The unit specifies whether you want the result in years (“y”), months (“m”), days (“d”), or combinations like months excluding years (“ym”) or days excluding months and years (“md”).

Anyone who works with dates in Excel, such as HR professionals tracking employee ages, demographers, or even individuals wanting to know their exact age in years, months, and days, should know how to calculate age in Excel using date of birth.

A common misconception is that simply subtracting two dates and dividing by 365 will give an accurate age. This doesn’t account for leap years correctly, nor does it easily break down the age into years, months, and days as `DATEDIF` does.

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

The core formula in Excel to calculate age is:

=DATEDIF(start_date, end_date, unit)

To get the age in years, months, and days, you combine multiple `DATEDIF` calls:

=DATEDIF(A1, B1, "y") & " years, " & DATEDIF(A1, B1, "ym") & " months, " & DATEDIF(A1, B1, "md") & " days"

Where A1 contains the date of birth and B1 contains the current or end date.

• DATEDIF(A1, B1, "y"): Calculates the number of full years between the two dates.
• DATEDIF(A1, B1, "ym"): Calculates the number of full months remaining after subtracting the full years.
• DATEDIF(A1, B1, "md"): Calculates the number of days remaining after subtracting full years and full months.

The `DATEDIF` function internally handles the complexities of different month lengths and leap years to give an accurate difference according to the specified unit.

Variables Table

Variable	Meaning	Unit	Typical range
start_date	The earlier date (e.g., Date of Birth)	Date	Any valid Excel date
end_date	The later date (e.g., Today’s Date)	Date	Any valid Excel date after start_date
unit	The unit for the result (“y”, “m”, “d”, “ym”, “md”, “yd”)	Text	“y”, “m”, “d”, “ym”, “md”, “yd”

Practical Examples (Real-World Use Cases)

Example 1: Calculating a Person’s Age Today

Suppose a person was born on August 15, 1990, and today’s date is March 5, 2024.

• Start Date (A1): 1990-08-15
• End Date (B1): 2024-03-05

Using the formula =DATEDIF(A1, B1, "y") & " years, " & DATEDIF(A1, B1, "ym") & " months, " & DATEDIF(A1, B1, "md") & " days", Excel would output: 33 years, 6 months, 19 days.

Example 2: Calculating Age at a Specific Past Date

What was the age of someone born on December 1, 2005, as of January 10, 2020?

• Start Date (A1): 2005-12-01
• End Date (B1): 2020-01-10

The formula would give: 14 years, 1 month, 9 days. This shows how you can calculate age in Excel using date of birth for any two dates.

How to Use This Calculate Age in Excel Using Date of Birth Calculator

1. Enter Date of Birth: Select the date of birth using the date picker for “Date of Birth”.
2. Enter Calculation Date: The “Calculation Date” defaults to today. You can change it to any other date to calculate the age as of that specific day.
3. Calculate: Click the “Calculate Age” button (though it updates automatically on date change).
4. Read Results: The primary result shows the age in years, months, and days. Intermediate results show total days, approximate total months, and total years as a decimal. The Excel formula used is also displayed.
5. View Chart: The bar chart visually breaks down the age.
6. Reset/Copy: Use “Reset” to clear and set default dates, or “Copy Results” to copy the age details.

Understanding the output helps you know the precise age, which is crucial for various applications where age matters down to the day.

Key Factors That Affect Calculate Age in Excel Using Date of Birth Results

• Start Date (Date of Birth): This is the anchor point. An incorrect birth date will lead to an incorrect age.
• End Date (Calculation Date): The age is calculated *as of* this date. Changing it changes the calculated age.
• The `unit` Argument in DATEDIF: Using “y”, “ym”, or “md” gives different parts of the age breakdown. Understanding these is vital to calculate age in Excel using date of birth accurately.
• Leap Years: `DATEDIF` correctly accounts for leap years (like February 29th) when calculating the difference in days and subsequently years and months. Manual calculations often miss this.
• Excel’s Date System: Excel stores dates as serial numbers. While `DATEDIF` handles this, being aware helps in troubleshooting.
• Time Component of Dates: `DATEDIF` generally ignores the time part of a date-time value, focusing only on the date portion for age calculation. If time precision were needed, other methods would be required.

Frequently Asked Questions (FAQ)

1. What is the DATEDIF function in Excel?

The `DATEDIF` function is an Excel function used to calculate the number of days, months, or years between two dates.

2. Why can’t I find DATEDIF in Excel’s function list?

It’s a “hidden” or “undocumented” function from Lotus 1-2-3 compatibility, but it works in most Excel versions. You just type it in.

3. How do I get today’s date in Excel for the end date?

You can use the `TODAY()` function in the cell for the end date (e.g., `B1=TODAY()`).

4. Can DATEDIF calculate age in hours or minutes?

No, `DATEDIF` is limited to days, months, and years. For smaller units, you’d subtract the date-time values and multiply by 24 (for hours) or 24*60 (for minutes).

5. What happens if the start date is later than the end date?

In Excel, `DATEDIF` will return a `#NUM!` error if the start_date is greater than the end_date.

6. How accurate is DATEDIF for age calculation?

It’s very accurate for calculating age in full years, months, and days based on calendar dates.

7. Are there alternatives to DATEDIF to calculate age in Excel using date of birth?

Yes, you can use combinations of `YEAR`, `MONTH`, `DAY` functions and `IF` statements, or the `YEARFRAC` function for decimal years, but `DATEDIF` is generally the most straightforward for years, months, and days.

8. Does DATEDIF work in Google Sheets?

Yes, the `DATEDIF` function works similarly in Google Sheets to calculate age in excel using date of birth (or rather, Sheets).