Use Excel To Calculate Age

Excel Age Calculator

Enter the date of birth and the “as of” date to calculate the age, mirroring how you would use Excel to calculate age.

As of Date	Age (Years, Months, Days)

Table: Age at different future dates.

What is Using Excel to Calculate Age?

Using Excel to calculate age involves leveraging its built-in functions, primarily DATEDIF, to determine the duration between a date of birth and a specified “as of” date (often the current date). This is a common task in various fields, including HR, demographics, and data analysis, where knowing the precise age of individuals or the duration of events is crucial. Instead of manually counting years, months, and days, you can use Excel to calculate age quickly and accurately.

Anyone who works with dates and needs to find the age or duration between two dates should learn how to use Excel to calculate age. This includes HR professionals tracking employee ages, demographers studying population age structures, or even individuals wanting to know their exact age.

A common misconception is that simply subtracting the birth year from the current year is enough. However, this doesn’t account for the month and day, leading to inaccuracies. To accurately use Excel to calculate age, you need functions that consider the full dates.

Excel Formulas to Calculate Age and Mathematical Explanation

The most common and versatile way to use Excel to calculate age is with the DATEDIF function. Its syntax is DATEDIF(start_date, end_date, unit).

• start_date: The earlier date (e.g., date of birth).
• end_date: The later date (e.g., today’s date or the “as of” date).
• unit: The type of interval you want to return (“Y” for full years, “M” for full months, “D” for days, “YM” for months excluding years, “MD” for days excluding months and years, “YD” for days excluding years).

To get the age in years, months, and days, you combine these:

• Years: =DATEDIF(A1, B1, "Y") (assuming A1 is birth date, B1 is as of date)
• Months: =DATEDIF(A1, B1, "YM")
• Days: =DATEDIF(A1, B1, "MD")

You can then concatenate these for a full age string: =DATEDIF(A1, B1, "Y") & " years, " & DATEDIF(A1, B1, "YM") & " months, " & DATEDIF(A1, B1, "MD") & " days".

Another function, YEARFRAC, can give the age as a decimal year, but DATEDIF is better for years, months, and days.

Variables Table:

Variable	Meaning	Unit	Typical Range
start_date (Birth Date)	The beginning date of the period	Date	Valid Excel date
end_date (As of Date)	The ending date of the period	Date	Valid Excel date, usually >= start_date
“Y”	Unit for full years	Text	“Y”
“M”	Unit for full months	Text	“M”
“D”	Unit for full days	Text	“D”
“YM”	Unit for months after full years	Text	“YM”
“MD”	Unit for days after full months	Text	“MD”

Practical Examples (Real-World Use Cases)

Example 1: Calculating Employee Ages

An HR department needs to calculate the current age of all employees. They have a spreadsheet with employee birth dates in column B, starting from B2. Today’s date is July 22, 2024.

• Birth Date (Cell B2): 1985-03-15
• As of Date (Today): 2024-07-22

To use Excel to calculate age in years: =DATEDIF(B2, TODAY(), "Y") results in 39.

For full age: =DATEDIF(B2, TODAY(), "Y") & " years, " & DATEDIF(B2, TODAY(), "YM") & " months, " & DATEDIF(B2, TODAY(), "MD") & " days" results in “39 years, 4 months, 7 days”.

Example 2: Age Verification for a Service

A service requires users to be at least 18 years old. They need to check if a person born on 2006-11-05 is 18 as of today (July 22, 2024).

• Birth Date: 2006-11-05
• As of Date: 2024-07-22

Using =DATEDIF("2006-11-05", "2024-07-22", "Y") gives 17. The person is not yet 18.

How to Use This Age Calculator

This calculator mirrors the logic you would use in Excel to calculate age:

1. Enter Date of Birth: Select the date of birth using the date picker.
2. Enter As of Date: Select the date at which you want the age calculated. It defaults to today’s date, but you can change it.
3. Calculate: The age will update automatically as you change the dates. You can also click “Calculate Age”.
4. Read Results:
   • Primary Result: Shows the age in completed years.
   • Full Age: Shows years, months, and days.
   • Total Days/Months Old: Shows the total duration in days or months.
   • Excel Formulas Used: Shows the exact DATEDIF formulas you’d use in Excel.
5. Reset: Clears the inputs and results, setting “As of Date” back to today.
6. Copy Results: Copies the main results and formulas to your clipboard.

The table and chart show how the age progresses over different “As of Dates,” helping visualize age milestones.

Key Factors That Affect Age Calculation in Excel

1. Correct Date Format: Ensure both the birth date and the “as of” date are entered in a format Excel recognizes as a date (e.g., YYYY-MM-DD, MM/DD/YYYY). Incorrect formats lead to #VALUE! errors when you use Excel to calculate age.
2. The DATEDIF Function: While powerful, DATEDIF is an undocumented function in some Excel versions, but it generally works. Be aware of its behavior, especially with the “MD” unit around month-ends.
3. Leap Years: DATEDIF correctly accounts for leap years when calculating days (“D”) and the “MD” unit. Manual calculations might miss this.
4. Start and End Date Order: The start date (birth date) must be earlier than or the same as the end date (“as of” date) for DATEDIF to return a non-negative result without error.
5. The “As of” Date: The calculated age is always relative to the “as of” date. Changing this date changes the age. Using TODAY() in Excel makes it dynamic.
6. Time Component: Excel dates can include time. If your birth date or “as of” date has a time component, it usually doesn’t affect DATEDIF with “Y”, “M”, “YM”, or “MD” units, as these operate on whole days. However, direct subtraction (end_date – start_date) might yield a fractional number of days if times are different.

Frequently Asked Questions (FAQ)

How do I use Excel to calculate age in years only?

Use the formula =DATEDIF(birth_date, as_of_date, "Y"), replacing birth_date and as_of_date with the respective cell references or date values.

Can I use Excel to calculate age with fractions of a year?

Yes, you can use the YEARFRAC(start_date, end_date, [basis]) function. For example, =YEARFRAC(A1, TODAY()) will give the age as a decimal.

What if the birth date is after the “as of” date?

DATEDIF will return a #NUM! error if the start date is later than the end date. Ensure the birth date is before or the same as the “as of” date.

Is DATEDIF available in all versions of Excel?

DATEDIF is available in most versions of Excel (including Excel 2007, 2010, 2013, 2016, 2019, 2021, and Microsoft 365), but it’s often undocumented. It was originally from Lotus 1-2-3 for compatibility.

How does DATEDIF handle leap years when I use Excel to calculate age?

It correctly accounts for leap years when calculating the difference in days or using units like “MD” and “YD”.

Why does “MD” sometimes give unexpected results?

The “MD” unit calculates the difference in days ignoring months and years. Its behavior around the end of months, especially with differing month lengths, can sometimes seem non-intuitive but is consistent with how it’s designed. For example, the days between Jan 31 and Mar 1 might be calculated in a way that looks odd if you just look at the day numbers.

Can I calculate age from just the year of birth?

If you only have the year of birth, you can only estimate the age by subtracting the birth year from the current year. For a precise age using DATEDIF, you need the full date of birth.

How can I get the age in total months or total days?

Use =DATEDIF(birth_date, as_of_date, "M") for total months and =DATEDIF(birth_date, as_of_date, "D") for total days (or simply =as_of_date - birth_date formatted as a number for total days).

Related Tools and Internal Resources

• Date Difference Calculator: Calculate the number of days, months, and years between two dates.
• Days Between Dates Calculator: Find the exact number of days between any two dates.
• Add or Subtract Days from Date: Calculate a future or past date by adding or subtracting days.
• Working Days Calculator: Calculate the number of working days between two dates, excluding weekends and holidays.
• Age Calculator by Date of Birth: A general age calculator based on date of birth.
• Time Duration Calculator: Calculate the duration between two times or add/subtract time.