Age Calculator (Excel DATEDIF Style) – Calculate Age Using Excel

Calculate age in years, months, and days between two dates, similar to how you would calculate age using Excel’s DATEDIF function. Enter the birth date and the “as of” date below.

Breakdown:

The calculation mimics Excel’s DATEDIF(start_date, end_date, "y") for years, DATEDIF(start_date, end_date, "ym") for months after full years, and DATEDIF(start_date, end_date, "md") for days after full months.

Excel DATEDIF Unit Examples

Table showing age components based on different DATEDIF units for the entered dates.

DATEDIF Unit	Result	Description
“y”		Completed years
“m”		Completed months
“d”		Completed days
“ym”		Months remaining after full years
“yd”		Days remaining after full years (not months)
“md”		Days remaining after full months and years

What is Calculating Age Using Excel?

Calculating age using Excel refers to the process of determining the duration between a birth date and another date (usually the current date or a specific “as of” date) using Microsoft Excel’s functions and formulas. The most common and direct way to calculate age using Excel is with the DATEDIF function, although other methods involving date arithmetic also exist. This is useful for various applications like HR databases (employee age), school records (student age), or simply for personal use.

Many users want to calculate age using Excel to get the age in years, months, and days, which DATEDIF handles well. However, DATEDIF is a “hidden” or “undocumented” function in some Excel versions, meaning it might not appear in the function wizard, but it still works if typed directly.

Common misconceptions include thinking that simply subtracting dates and dividing by 365 is always accurate (it isn’t, due to leap years) or that DATEDIF is unreliable (it’s generally reliable but has known issues with the “md” unit under specific edge cases).

Calculating Age Using Excel: Formula and Mathematical Explanation

The primary function to calculate age using Excel is DATEDIF(start_date, end_date, unit).

• start_date: The earlier date (e.g., birth date).
• end_date: The later date (e.g., today’s date or the “as of” date).
• unit: The unit of time you want the result in:
  • “y”: Complete years between the dates.
  • “m”: Complete months between the dates.
  • “d”: Complete days between the dates.
  • “ym”: Months remaining after subtracting full years.
  • “yd”: Days remaining after subtracting full years (ignoring months).
  • “md”: Days remaining after subtracting full years and full months.

To get age in “X years, Y months, Z days”, you’d use:

• Years (X) = DATEDIF(birth_date, as_of_date, "y")
• Months (Y) = DATEDIF(birth_date, as_of_date, "ym")
• Days (Z) = DATEDIF(birth_date, as_of_date, "md")

Variables Table

Variable	Meaning	Unit	Typical Range
start_date	The beginning date (e.g., birth date)	Date	Valid Excel date
end_date	The ending date (e.g., today)	Date	Valid Excel date, after start_date
unit (“y”, “m”, “d”, etc.)	The unit for the result	Text	“y”, “m”, “d”, “ym”, “yd”, “md”

Another, less precise method to roughly calculate age using Excel in years is (end_date - start_date) / 365.25, but this gives a decimal and doesn’t handle month/day breakdowns accurately.

Practical Examples (Real-World Use Cases)

Example 1: Calculating Employee Age

An HR department needs to calculate the age of an employee born on June 15, 1985, as of December 31, 2023.

• Birth Date (start_date): 1985-06-15
• As of Date (end_date): 2023-12-31

Using DATEDIF:

• Years = DATEDIF("1985-06-15", "2023-12-31", "y") = 38 years
• Months = DATEDIF("1985-06-15", "2023-12-31", "ym") = 6 months
• Days = DATEDIF("1985-06-15", "2023-12-31", "md") = 16 days

The employee is 38 years, 6 months, and 16 days old as of Dec 31, 2023.

Example 2: Calculating Age of an Account

A bank wants to know the age of an account opened on January 20, 2020, as of today (let’s say today is March 10, 2024).

• Start Date: 2020-01-20
• End Date: 2024-03-10

Using DATEDIF to calculate age using Excel formulas:

• Years = DATEDIF("2020-01-20", "2024-03-10", "y") = 4 years
• Months = DATEDIF("2020-01-20", "2024-03-10", "ym") = 1 month
• Days = DATEDIF("2020-01-20", "2024-03-10", "md") = 20 days (or 19 depending on leap year handling by DATEDIF near month ends)

The account is 4 years, 1 month, and 20 days old.

How to Use This Age Calculator

This calculator helps you calculate age using Excel‘s DATEDIF logic without opening Excel.

1. Enter Birth Date: Select the date of birth using the date picker for “Birth Date”.
2. Enter “As of” Date: Select the date for which you want to calculate the age. It defaults to today’s date, but you can change it.
3. Calculate: The age will be calculated automatically as you change the dates, or you can click “Calculate Age”.
4. View Results:
   • The “Primary Result” shows the age in years, months, and days.
   • “Breakdown” shows completed years, total months, total days, and the Excel DATEDIF formulas you would use.
   • The table shows results for other DATEDIF units.
   • The chart visually compares years, total months, and total days.
5. Reset: Click “Reset” to set the dates back to default values (today for “As of Date”, and clears birth date).
6. Copy Results: Click “Copy Results” to copy the main age and breakdown to your clipboard.

The results mirror how you would calculate age using Excel, specifically the DATEDIF function for “y”, “ym”, and “md” units.

Key Factors That Affect Age Calculation Results

1. Start Date (Birth Date): The accuracy of the birth date is crucial. An incorrect day, month, or year will lead to an incorrect age.
2. End Date (“As of” Date): The age is calculated up to this date. Changing it changes the age.
3. Leap Years: The number of leap days between the two dates affects the total number of days and can influence month/day calculations, especially around February 29th. DATEDIF inherently handles leap years correctly for “y”, “m”, and “d” units.
4. The Unit Used (“y”, “m”, “d”, “ym”, “yd”, “md”): Different units give different perspectives on the duration. “y” gives full years, “ym” gives months past the full years, etc.
5. Excel’s DATEDIF Implementation: While generally reliable, DATEDIF with the “md” unit has known issues in some very specific date combinations (e.g., around month-ends before leap days), which our calculator tries to mimic. To calculate age using Excel reliably, be aware of these.
6. Time Component (Not Used Here): Excel dates can include time. If time was considered, it would add another layer of precision, but DATEDIF and this calculator ignore the time part, focusing only on the date.

Frequently Asked Questions (FAQ)

1. How do I calculate age in Excel if DATEDIF is not visible?

Even if DATEDIF doesn’t show up in Excel’s function suggestions, you can usually type it directly into a cell, like =DATEDIF(A1, B1, "y"), and it will work in most versions.

2. What’s the most accurate way to calculate age in years as a decimal in Excel?

=YEARFRAC(start_date, end_date, 1) is more accurate than (end_date - start_date)/365.25 as it considers the actual days in the years between the dates based on the day count basis (1 = actual/actual).

3. Can I calculate age in just total months or total days using DATEDIF?

Yes, use =DATEDIF(start_date, end_date, "m") for total months and =DATEDIF(start_date, end_date, "d") for total days.

4. Why does DATEDIF with “md” sometimes give negative or incorrect results?

The “md” unit in DATEDIF has known bugs, particularly when the day of the start date is greater than the day of the end date, especially around February. This is a limitation of the function itself when you calculate age using Excel‘s DATEDIF.

5. How can I calculate someone’s age on a specific future date in Excel?

Use the birth date as the start_date and the specific future date as the end_date in the DATEDIF function or other date calculations.

6. Is there an alternative to DATEDIF to calculate age in years, months, and days in Excel?

While DATEDIF is the most direct, you can build complex formulas using YEAR, MONTH, DAY, and IF functions to calculate each component, but it’s much more complicated to get the month and day rollovers right.

7. How do I calculate age using Excel from a date of birth in one cell and today’s date?

If the birth date is in cell A1, use =DATEDIF(A1, TODAY(), "y") for years, =DATEDIF(A1, TODAY(), "ym") for months, and =DATEDIF(A1, TODAY(), "md") for days.

8. Does this calculator handle leap years when calculating age?

Yes, the logic mimics DATEDIF, which correctly accounts for leap years when calculating the number of full years, months, and days between two dates.