Age Calculator: Calculate Age from Date of Birth in Excel using Today

Age Calculator from Date of Birth

A precise tool to calculate age from date of birth in Excel using today‘s date as the reference.

Enter Your Date of Birth

Select your date of birth to calculate your current age.

Age Summary in Different Units
Unit	Value
Years	0
Months	0
Days	0
Total Weeks	0
Total Hours	0
Total Minutes	0
Total Seconds	0

What is an Age Calculation?

An age calculation determines the time that has passed from a person’s date of birth to a specific end date, which is typically today. While it seems simple, precision matters, especially when dealing with professional contexts like HR records or financial applications. The core challenge lies in handling the varying lengths of months and the occurrence of leap years. For those who frequently work with spreadsheets, learning to calculate age from date of birth in Excel using today is a fundamental and highly valuable skill.

The Formula to Calculate Age from Date of Birth in Excel using Today

The most accurate and reliable method to calculate age in Excel is by using the hidden DATEDIF function. This function is specifically designed to find the difference between two dates in various units like years, months, or days. While other methods exist, such as dividing the total days by 365.25, they can introduce small inaccuracies.

The primary formula to find the number of completed years is:

=DATEDIF(start_date, end_date, "Y")

Formula Variables Explained

Variable	Meaning	Unit (in Excel)	Typical Range
`start_date`	The person’s date of birth.	A valid Excel date (e.g., a cell like A2).	Any valid past date.
`end_date`	The date on which to calculate the age. Often `TODAY()`.	A valid Excel date (e.g., `TODAY()`).	A date after the start_date.
`"Y"`	The unit specifier, telling `DATEDIF` to count full years.	Text String (“Y”, “YM”, “MD”).	“Y” for years, “M” for total months, “D” for total days.

To get a more detailed age, you can combine functions: =DATEDIF(A2, TODAY(), "Y") & " years, " & DATEDIF(A2, TODAY(), "YM") & " months, " & DATEDIF(A2, TODAY(), "MD") & " days".

Practical Examples

Example 1: Calculating a Person’s Age

Input (Date of Birth): January 15, 1990
Input (End Date): Today
Excel Formula: =DATEDIF("1990-01-15", TODAY(), "Y")
Result: The formula will return the number of full years the person has lived.

Example 2: Calculating an Infant’s Age in Months and Days

Input (Date of Birth): October 5, 2023
Input (End Date): Today
Excel Formula (Years): =DATEDIF("2023-10-05", TODAY(), "Y")
Excel Formula (Months): =DATEDIF("2023-10-05", TODAY(), "YM")
Result: This will show the age in years and the remaining months, perfect for tracking an infant’s age. For more detail, check out this birthday calculator.

How to Use This Age Calculator

Enter the Date of Birth: Click on the input field and use the calendar to select the date of birth.
View the Result: The calculator automatically updates, showing the age in years, months, and days. No need to click ‘Calculate’ unless you change the date manually.
Analyze the Breakdown: The table and chart below provide the age in different units like total weeks, days, hours, and more for a comprehensive view.
Copy or Reset: Use the “Copy Results” button to save the output to your clipboard or “Reset” to clear the fields. For spreadsheet enthusiasts, learning the Excel age formula is a great next step.

Key Factors That Affect Age Calculation

Leap Years: A proper calculation must account for the extra day in a leap year (February 29th). The DATEDIF function handles this automatically.
Time of Day: Our calculator, like Excel’s TODAY() function, does not consider the time of birth. It calculates based on whole days.
End Date: Changing the end date from “today” to a future or past date will, of course, change the calculated age.
Incomplete Months: The number of days in a month varies (28, 29, 30, or 31), which is the primary reason simple division-based formulas fail.
The “MD” Unit in DATEDIF: There is a known bug with the “MD” unit in Excel’s DATEDIF that can sometimes produce incorrect results. This calculator uses a more reliable JavaScript implementation.
Cultural Differences: Some cultures calculate age differently (e.g., being “age 1” at birth). This tool uses the standard Western method, where you are “age 0” until your first birthday. Understanding how to find age from DOB is crucial for accuracy.

Frequently Asked Questions (FAQ)

1. What is the best formula to calculate age from date of birth in Excel?: The most accurate formula is =DATEDIF(birth_date, TODAY(), "Y") for years. Other methods can be less precise.
2. Why can’t I just subtract the dates and divide by 365?: This method doesn’t account for leap years, leading to small but accumulating errors over time. Using a function like DATEDIF or YEARFRAC is better.
3. How do I calculate age in years, months, and days in Excel?: You use three separate DATEDIF functions with the units “Y”, “YM” (months after years), and “MD” (days after months) and concatenate the results.
4. How does this calculator handle leap years?: The underlying JavaScript logic correctly accounts for leap years by using date objects, which inherently understand the Gregorian calendar rules, ensuring an accurate age calculation in spreadsheets.
5. Can I calculate someone’s age on a future date?: Yes. While this tool defaults to today, in Excel you can replace TODAY() with any specific date, like =DATEDIF(A2, "2030-12-31", "Y").
6. Is the DATEDIF function available in all versions of Excel?: Yes, but it’s often undocumented because it was included for compatibility with Lotus 1-2-3. It works in all modern versions of Excel.
7. What does “YM” mean in the DATEDIF formula?: It calculates the number of complete months between two dates after subtracting the full years, which is useful for finding the “months” part of an age.
8. How can I copy the results?: Click the “Copy Results” button. This will copy a detailed summary of your calculated age to your clipboard, ready to be pasted elsewhere.

Related Tools and Internal Resources

Explore more of our calculators and resources to master your data skills:

Exact Age Calculator: A tool similar to this one with even more detailed breakdowns.
Date Difference Calculator: Calculate the duration between any two dates, not just from a date of birth.