How To Calculate Age In Excel Using Date Of Birth

Easily determine age in years, months, and days from a date of birth, similar to Excel’s DATEDIF function. Learn how to calculate age in Excel using date of birth below.

Age Calculator

Understanding the Age Calculation

What is Calculating Age in Excel Using Date of Birth?

Calculating age in Excel using a date of birth involves determining the duration between the birth date and a specified end date (often today’s date) in terms of years, months, and days. The most common way to **how to calculate age in excel using date of birth** is by using the `DATEDIF` function. This function is specifically designed to calculate the difference between two dates in various units.

Anyone who needs to find the precise age of an individual or the duration between two dates can use this method. This is common in HR, demographics, event planning, and many data analysis scenarios. A common misconception is that simply subtracting the birth year from the current year gives the correct age; while close, it doesn’t account for months and days, which `DATEDIF` handles accurately when you want to **how to calculate age in excel using date of birth**.

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

The core formula used in Excel to **how to calculate age in excel using date of birth** is:

=DATEDIF(start_date, end_date, unit)

Where:

• start_date: The earlier date (e.g., the date of birth).
• end_date: The later date (e.g., today’s date or the date at which you want to calculate the age).
• unit: The unit of time you want the result in. Common units for age calculation are:
  • "Y": The number of complete years in the period.
  • "M": The number of complete months in the period.
  • "D": The number of days in the period.
  • "YM": The number of complete months after subtracting the full years.
  • "MD": The number of days after subtracting full years and full months.
  • "YD": The number of days between the dates as if they were in the same year (ignoring years).

DATEDIF Unit Arguments

Unit	Meaning	Returns	Typical Range
“Y”	Years	Completed years between dates	0+
“M”	Months	Completed months between dates	0+
“D”	Days	Days between dates	0+
“YM”	Months excluding years	Completed months remaining after years	0-11
“MD”	Days excluding years and months	Days remaining after years and months	0-30/31
“YD”	Days excluding years	Days as if dates were in the same year	0-365

To get the age in years, months, and days, you typically use `DATEDIF` three times: once with “Y”, once with “YM”, and once with “MD”.

Practical Examples

Let’s see **how to calculate age in excel using date of birth** with some examples.

Example 1: Calculating Age Today

Suppose someone was born on June 15, 1990, and today’s date is October 26, 2023.

• =DATEDIF("1990-06-15", "2023-10-26", "Y") returns 33 (years)
• =DATEDIF("1990-06-15", "2023-10-26", "YM") returns 4 (months)
• =DATEDIF("1990-06-15", "2023-10-26", "MD") returns 11 (days)

So, the age is 33 years, 4 months, and 11 days.

Example 2: Calculating Age at a Specific Date

Someone was born on December 1, 2005, and we want to know their age on January 1, 2024.

• =DATEDIF("2005-12-01", "2024-01-01", "Y") returns 18 (years)
• =DATEDIF("2005-12-01", "2024-01-01", "YM") returns 1 (month)
• =DATEDIF("2005-12-01", "2024-01-01", "MD") returns 0 (days)

Their age on January 1, 2024, will be 18 years and 1 month.

How to Use This Age Calculator

Our calculator simplifies the process of finding age based on a date of birth:

1. Enter Date of Birth: Select the date of birth using the date picker for the “Date of Birth” field.
2. Enter ‘As Of’ Date: The “Calculate Age As Of” field defaults to today’s date. You can change it to calculate age at any specific point in time.
3. Calculate: The calculator automatically updates the age as you input the dates. You can also click the “Calculate Age” button.
4. View Results: The primary result shows the age in Years, Months, and Days. Intermediate results show total days, approximate total months, and approximate total years.
5. Reset: Click “Reset” to clear the dates and set the ‘As Of’ date back to today.
6. Copy Results: Click “Copy Results” to copy the age details to your clipboard.

The results help you understand the precise age down to the day.

Key Factors That Affect Age Calculation Results

• Date of Birth: This is the starting point. An accurate date of birth is crucial for an accurate age calculation.
• ‘As Of’ Date: The age is calculated up to this date. Changing this date changes the resulting age.
• Leap Years: The calculation correctly accounts for leap years when determining the number of days. Our calculator and Excel’s `DATEDIF` handle this.
• Time of Birth vs. Time of ‘As Of’ Date: `DATEDIF` and our calculator work with whole dates. We don’t consider the time of day, so the age is based on the start of the ‘As Of’ date.
• Date Format Ambiguity: Ensure dates are entered in a non-ambiguous format (like YYYY-MM-DD used by the date picker) to avoid misinterpretation, especially when manually entering into Excel.
• Excel’s `DATEDIF` Quirks: While powerful, `DATEDIF` has known quirks, especially with the “MD” unit under certain date combinations, though it’s generally reliable for age. Our calculator aims for similar logic.

Frequently Asked Questions (FAQ)

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

You can only calculate the approximate age in years by subtracting the birth year from the current year (e.g., `YEAR(TODAY()) – birth_year`). For exact age, you need the full date of birth.

Is the `DATEDIF` function available in all versions of Excel?

Yes, `DATEDIF` is available in almost all versions of Excel, but it’s often undocumented and doesn’t appear in the function list or help files in some older versions. However, it still works.

How can I calculate the age in total months or total days in Excel?

Use `DATEDIF(start_date, end_date, “M”)` for total months and `DATEDIF(start_date, end_date, “D”)` for total days.

Why does `DATEDIF` sometimes give unexpected results with “MD”?

There are known edge cases with “MD” in `DATEDIF`, particularly when the day of the `start_date` is greater than the day of the `end_date` in the final month. Our calculator uses a robust JavaScript method to minimize these issues.

Can I calculate age from a date of birth stored as text in Excel?

If the date is text but looks like a date (e.g., “15-06-1990”), you might need to convert it to a real date using `DATEVALUE` or by re-entering before `DATEDIF` can use it effectively. `DATEDIF(DATEVALUE(“15-06-1990”), TODAY(), “Y”)`.

How does the calculator handle leap years?

The age calculation logic, both in Excel’s `DATEDIF` and our JavaScript calculator, correctly accounts for the extra day in leap years when calculating the total number of days and the breakdown into years, months, and days.

Can I use this to find the difference between any two dates, not just age?

Yes, absolutely. The `DATEDIF` function and our calculator can find the duration between any two dates in years, months, and days.

What if the ‘As of Date’ is before the ‘Date of Birth’?

The calculator and `DATEDIF` expect the `start_date` (Date of Birth) to be earlier than the `end_date` (‘As Of’ Date). If not, you’ll likely get an error or non-sensical results. Our calculator will show an error message.