Calculate Age in Excel Using DOB

A web-based tool to instantly find an exact age, and a complete guide on how to perform the same calculation within an Excel spreadsheet using the DATEDIF formula.

Instant Age Calculator

Age Breakdown in Different Units

Unit	Total
Total Years (Decimal)
Total Months
Total Weeks
Total Days

What is “Calculate Age in Excel Using DOB”?

To “calculate age in Excel using DOB” means to determine a person’s age based on their date of birth (DOB) within a Microsoft Excel spreadsheet. This is a very common task for HR professionals, data analysts, event planners, and anyone managing datasets with personal information. Excel does not have a single “AGE” function, but it provides a powerful, albeit somewhat hidden, function called DATEDIF that is perfect for this task. This function allows you to find the difference between two dates in complete years, months, or days.

The Excel Age Calculation Formula and Explanation

The primary formula used to calculate age in Excel is =DATEDIF(start_date, end_date, unit). This function takes a start date (the date of birth), an end date (usually today’s date), and a specific unit to return the result.

To get a person’s complete age in years, the formula is: =DATEDIF(A2, TODAY(), "Y"). In this formula, A2 is the cell containing the date of birth, TODAY() is an Excel function that returns the current date, and "Y" tells DATEDIF to count the number of full years between the two dates.

DATEDIF Unit Variables

Unit arguments for the DATEDIF function

Variable	Meaning	Unit	Typical Range
“Y”	Calculates the number of complete years.	Years	0-120
“M”	Calculates the number of complete months.	Months	0-1440
“D”	Calculates the total number of days.	Days	0-43800
“YM”	Calculates the number of months, ignoring years.	Months	0-11
“YD”	Calculates the number of days, ignoring years.	Days	0-364
“MD”	Calculates the number of days, ignoring years and months.	Days	0-30

For more details on these functions, you might want to look into the {related_keywords}. You can find more info at {internal_links}.

Practical Examples

Example 1: Simple Age in Years

Let’s say a person’s date of birth, July 30, 2002, is in cell A2. You want to find their current age in completed years.

• Input (A2): 07/30/2002
• Formula: =DATEDIF(A2, TODAY(), "Y")
• Result: The formula will return the number of full years that have passed since their birth date.

Example 2: Exact Age in Years, Months, and Days

To get a more detailed age like “21 years, 5 months, and 15 days”, you need to combine three DATEDIF functions using concatenation (&).

• Input (A2): 07/30/2002
• Formula: =DATEDIF(A2, TODAY(), "Y") & " years, " & DATEDIF(A2, TODAY(), "YM") & " months, " & DATEDIF(A2, TODAY(), "MD") & " days"
• Result: This string will display the full, detailed age. Each part of the formula calculates a different component of the age. This is a common task in {related_keywords}, and more information can be found at {internal_links}.

How to Use This Age Calculator

Our web-based calculator simplifies the process, giving you an instant answer without needing to open Excel.

1. Enter Date of Birth: Use the date picker to select the person’s date of birth.
2. Enter ‘As of’ Date: This field automatically populates with today’s date. You can change it to any date to calculate age at a specific moment in time (e.g., age at the time of an event).
3. Calculate: Click the “Calculate Age” button.
4. Interpret Results: The calculator will show the primary result as years, months, and days. It will also provide a table with the age converted into various total units like total days, total months, etc.

Key Factors That Affect Age Calculation in Excel

• Leap Years: The DATEDIF function automatically handles leap years, making it more accurate than simply dividing total days by 365.25.
• The TODAY() Function: Using TODAY() makes your age calculation dynamic. The result will automatically update every time you open the workbook.
• Start and End Dates: The start_date (DOB) must be earlier than the end_date. If not, the formula will return a #NUM! error.
• Cell Formatting: Ensure that the cells containing your dates are formatted as ‘Date’ in Excel. If they are formatted as text, the formula will fail. For topics like the {related_keywords}, proper formatting is crucial. See {internal_links} for guides.
• The “MD” Unit Bug: The “MD” argument in DATEDIF is known to have some issues, occasionally returning negative numbers or incorrect values, especially with dates near the end of the month. Using it requires caution.
• Alternative Functions: For some cases, like finding age as a decimal, the YEARFRAC function can be useful. The formula =YEARFRAC(A2, TODAY()) returns the age as a fractional number (e.g., 21.5).

Frequently Asked Questions (FAQ)

How do I calculate age in Excel without DATEDIF?

You can subtract the birth date from the current date and divide by 365.25 (e.g., =(TODAY()-A2)/365.25). However, this is less accurate than DATEDIF. Wrapping it in an INT function (=INT((TODAY()-A2)/365.25)) gives the completed years.

Why is my DATEDIF formula giving a #NUM! error?

This usually happens if the start date in your formula is later than the end date. Double-check your date entries.

How can I calculate age for a whole column of birthdays?

Write the formula in the first cell, then click and drag the fill handle (the small square at the bottom-right corner of the cell) down the column to apply the formula to all other cells.

Can I calculate age as of a specific date, not today?

Yes. Instead of using TODAY() as the end date, enter the specific date in another cell (e.g., B2) and reference it in your formula: =DATEDIF(A2, B2, "Y").

Does the DATEDIF function work in Google Sheets?

Yes, the DATEDIF function works exactly the same in Google Sheets as it does in Excel, so you can use the same formulas.

Why is DATEDIF a “hidden” function in Excel?

Excel includes DATEDIF for compatibility with older spreadsheet programs like Lotus 1-2-3. It is not officially documented and does not appear in the function autocomplete list, but it is fully functional.

What’s the difference between using “Y” and “YD”?

“Y” calculates the total number of full years. “YD” calculates the number of days between two dates as if they were in the same year, ignoring the year component. It’s useful for calculating birthday anniversaries.

How does Excel handle date formats from different regions?

Excel can be tricky with regional date formats (e.g., MM/DD/YYYY vs DD/MM/YYYY). It’s best to ensure your computer’s system settings and Excel’s cell formats are consistent to avoid errors. This is a common issue when dealing with {related_keywords} from international sources. Find out more at {internal_links}.

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