Age Calculator for Excel (DATEDIF)

Easily calculate age or duration between two dates, just like using the DATEDIF function in Excel. Find out how to calculate age using Excel’s methods below.

Unit	Description	Result
Enter dates and click calculate to see results.

Table showing age calculation with different units.

What is Calculating Age in Excel?

Calculating age in Excel involves finding the difference between two dates, typically a birth date and a reference date (like today’s date or a specific event date). Excel provides the `DATEDIF` function specifically for this purpose, although it’s somewhat “hidden” and not always listed in function wizards. Knowing how to calculate age using Excel is useful in various scenarios, from HR databases to demographic studies and simple birthday tracking.

The core of how to calculate age using Excel lies in the `DATEDIF(start_date, end_date, unit)` function. It can return the difference in completed years (“Y”), months (“M”), days (“D”), or combinations like months after years (“YM”), days after years (“YD”), and days after months and years (“MD”).

Who Should Use It?

Anyone who needs to find the duration between two dates in years, months, or days can benefit from learning how to calculate age using Excel. This includes HR professionals, project managers, demographers, researchers, and even individuals managing personal data.

Common Misconceptions

A common misconception is that you can simply subtract two dates and divide by 365 to get the age in years. While this gives an approximation, it doesn’t accurately account for leap years, leading to errors. The `DATEDIF` function, when used correctly, handles these complexities accurately, which is crucial for precise age calculation.

How to Calculate Age Using Excel: Formula and Explanation

The primary method for how to calculate age using Excel is the `DATEDIF` function. Its syntax is:

=DATEDIF(start_date, end_date, unit)

• start_date: The earlier date (e.g., birth date). This must be a valid Excel date.
• end_date: The later date (e.g., today’s date or the date at which you want to calculate age). This also must be a valid Excel date, and it must be later than or equal to the start_date.
• unit: A text string specifying the unit of time you want the difference to be returned in:
  • “Y”: Completed years between the dates.
  • “M”: Completed months between the dates.
  • “D”: Completed days between the dates.
  • “MD”: Days remaining after subtracting full months (and years). Useful for “X years, Y months, Z days”.
  • “YM”: Months remaining after subtracting full years. Useful for “X years, Y months”.
  • “YD”: Days remaining after subtracting full years (as if the dates were within the same year). Not always intuitive.

For example, if cell A1 contains the birth date (15-Mar-1990) and B1 contains today’s date (or you use `TODAY()`), to find the age in years, you’d use: `=DATEDIF(A1, B1, “Y”)` or `=DATEDIF(A1, TODAY(), “Y”)`.

Variables Table

Variable	Meaning	Unit	Typical Range/Format
start_date	The beginning date (e.g., date of birth)	Date	Valid Excel date format (e.g., YYYY-MM-DD, MM/DD/YYYY)
end_date	The ending date (e.g., current date)	Date	Valid Excel date format, >= start_date
unit	The unit for the result	Text	“Y”, “M”, “D”, “MD”, “YM”, “YD”

Variables used in the DATEDIF function for age calculation.

Practical Examples of How to Calculate Age Using Excel

Example 1: Calculating Age in Years, Months, and Days

Suppose someone was born on March 15, 1990, and we want to find their age as of June 1, 2024.

• Start Date: 1990-03-15
• End Date: 2024-06-01

In Excel:

• Years: `=DATEDIF(“1990-03-15”, “2024-06-01”, “Y”)` results in 34
• Months after years: `=DATEDIF(“1990-03-15”, “2024-06-01”, “YM”)` results in 2
• Days after months: `=DATEDIF(“1990-03-15”, “2024-06-01”, “MD”)` results in 17

So, the person is 34 years, 2 months, and 17 days old.

Example 2: Calculating Service Duration

An employee started on October 20, 2018, and we want to know their total service duration in months as of July 15, 2024.

• Start Date: 2018-10-20
• End Date: 2024-07-15

In Excel:

• Total Months: `=DATEDIF(“2018-10-20”, “2024-07-15”, “M”)` results in 68

The employee has completed 68 months of service.

How to Use This Age Calculator

Our calculator simplifies how to calculate age using Excel‘s `DATEDIF` logic:

1. Enter Start Date: Input the earlier date, like the date of birth, in the “Start Date” field.
2. Enter End Date: Input the later date, up to which you want to calculate the age or duration, in the “End Date” field. It defaults to today’s date.
3. Select Unit: Choose the desired unit (“Y”, “M”, “D”, “YM”, “YD”, “MD”) from the dropdown menu to specify how you want the result displayed.
4. Calculate: Click the “Calculate Age” button.
5. View Results: The primary result according to your selected unit will be shown prominently, along with intermediate calculations for full years, months, and days, and the equivalent DATEDIF formula. The table and chart will also update.
6. Reset: Click “Reset” to clear the inputs and results to their default state.
7. Copy Results: Click “Copy Results” to copy the main result and intermediate values to your clipboard.

Understanding the “Unit” is key to interpreting the results correctly when learning how to calculate age using Excel or this tool.

Key Factors That Affect Age Calculation Results

When you learn how to calculate age using Excel or use any age calculator, several factors influence the accuracy and interpretation of the results:

1. Accuracy of Dates: The start and end dates must be correct. An incorrect birth date will lead to an incorrect age.
2. End Date Specificity: The age is calculated *as of* the end date. Changing the end date changes the age.
3. Unit Selection (“Y”, “M”, “D”, etc.): The unit determines what the result represents (full years, total months, days within a month/year, etc.). Misinterpreting the unit leads to misunderstanding the result.
4. Leap Years: `DATEDIF` correctly handles leap years when calculating the difference in days or when boundary conditions involve February 29th. Simple subtraction and division by 365 or 365.25 don’t always get it right.
5. Start Date vs. End Date: The start date must be earlier than or equal to the end date for `DATEDIF` to work without error in Excel (or for logical results here).
6. Time Component (Ignored): Excel dates can have time components, but `DATEDIF` and this calculator typically consider only the date part, effectively assuming the time is midnight at the start of the day. If time is crucial, more complex calculations are needed.

Being mindful of these factors ensures you get meaningful results when figuring out how to calculate age using Excel‘s methods.

Frequently Asked Questions (FAQ)

1. What is the DATEDIF function in Excel?

The `DATEDIF` function calculates the number of days, months, or years between two dates. It’s a key tool for how to calculate age using Excel but isn’t always fully documented.

2. Why can’t I just subtract dates and divide by 365?

Subtracting dates gives the number of days. Dividing by 365 gives an approximate number of years but doesn’t perfectly account for leap years, leading to slight inaccuracies over long periods. `DATEDIF` with “Y” is more accurate for full years.

3. How do I calculate age in years, months, and days in Excel?

You use `DATEDIF` three times: once with “Y” for years, once with “YM” for months after years, and once with “MD” for days after months and years. For example: `=DATEDIF(A1,B1,”Y”) & ” years, ” & DATEDIF(A1,B1,”YM”) & ” months, ” & DATEDIF(A1,B1,”MD”) & ” days”`.

4. What does “YM”, “YD”, and “MD” mean in DATEDIF?

“YM” gives months excluding years, “YD” gives days excluding years (as if dates were in the same year), and “MD” gives days excluding full months and years.

5. Can DATEDIF handle dates before 1900?

Excel’s date system officially starts from January 1, 1900 (or 1904 on Mac if set). `DATEDIF` might not work reliably with dates before this, or it might require the 1904 date system to be enabled.

6. What if the end date is before the start date?

In Excel, `DATEDIF` will return a `#NUM!` error if the start_date is later than the end_date. Our calculator will show an error or zero/negative results depending on the context if dates are inverted.

7. How does this calculator relate to how to calculate age using Excel?

This calculator implements the same logic as Excel’s `DATEDIF` function, allowing you to get the same results you would expect in an Excel spreadsheet.

8. Is DATEDIF available in all versions of Excel?

Yes, `DATEDIF` has been available since at least Excel 2000, but it’s often not listed in the function help or autocomplete features. You have to type it in directly.