Please Note: This article is written for users of the following Microsoft Excel versions: 97, 2000, 2002, and 2003. If you are using a later version (Excel 2007 or later), this tip may not work for you. For a version of this tip written specifically for later versions of Excel, click here: Calculating Fractions of Years.

Calculating Fractions of Years

by Allen Wyatt
(last updated January 24, 2015)


One of the types of data that Excel allows you to store is, of course, dates. At some point you may wish to perform some calculations with the dates in your worksheet. It is not uncommon to need to figure out the percentage of a year represented by the difference between two dates. Excel allows you to calculate this easily using the YEARFRAC worksheet function. This function is part of the Analysis ToolPak provided with Excel.

To use the function, all you need to do is provide two dates and a value that specifies how Excel should calculate the fractional year:

=YEARFRAC(DateOne, DateTwo, Basis)

The dates used by YEARFRAC can be either static dates, or they can be references to cells that contain dates. The Basis value ranges between 0 and 4, with 0 being the default. The following are the different meanings for the Basis:

Basis Meaning
0 US 30/360
1 Actual/actual
2 Actual/360
3 Actual/365
4 European 30/360

You should note that if the YEARFRAC function does not work on your system, it means you have not installed or enabled the Analysis ToolPak. To enable it, follow these steps:

  1. Choose Add-Ins from the Tools menu. Excel displays the Add-Ins dialog box.
  2. Make sure the Analysis ToolPak option is selected.
  3. Click on OK.

If you did not see an Analysis ToolPak option in step 2, it means that you did not install the option when you first installed Excel. You can rerun the Excel Setup program and choose to install the option. You must then enable the add-in, and you can use the function.

ExcelTips is your source for cost-effective Microsoft Excel training. This tip (2562) applies to Microsoft Excel 97, 2000, 2002, and 2003. You can find a version of this tip for the ribbon interface of Excel (Excel 2007 and later) here: Calculating Fractions of Years.

Author Bio

Allen Wyatt

With more than 50 non-fiction books and numerous magazine articles to his credit, Allen Wyatt is an internationally recognized author. He  is president of Sharon Parq Associates, a computer and publishing services company. ...


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What is six more than 8?

2016-07-23 07:01:55


I have now resolved the issue. Somehow the add-ins for CSAPak had been unchecked. I have now checked them again.

2016-07-22 14:39:23


If this is exactly how you have it entered then a couple of parentheses (on end) were probably deleted inadvertently



It works in my version anyway Excel 2007

2016-07-20 03:18:31


I had a formula in Excel 2003 which I entered only a few weeks ago. Today the formula returns a #NAME? error. It doesn't recognise "=YEARFRAC" anymore, but only when used with the "TODAY()" value. The result takes a person's date of birth from today's date to give an age in Number to 2 decimal places as formatted for the cell.


This works in Google Spreadsheets. I uploaded to same spreadsheet to Google where it works without errors. Until recently it worked for Excel 2003.

An alternative formula for those who have died using the YEARFRAC value like
"=YEARFRAC(B$,C4)" taking the person's date of birth and date of death to return an age in 2 decimal places still works.

Does Microsoft kludge their older programs in their periodic updates to force users to upgrade?

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