Yearfrac function

This article describes the formula syntax and usage of the YEARFRAC function in Microsoft Excel.

Description

YEARFRAC calculates the fraction of the year represented by the number of whole days between two dates (the start_date and the end_date). For instance, you can use YEARFRAC to identify the proportion of a whole year's benefits, or obligations to assign to a specific term.

Syntax

YEARFRAC(start_date, end_date, [basis])

The YEARFRAC function syntax has the following arguments:

• Start_date    Required. A date that represents the start date.

• End_date    Required. A date that represents the end date.

• Basis    Optional. The type of day count basis to use.

Basis	Day count basis
0 or omitted	US (NASD) 30/360
1	Actual/actual
2	Actual/360
3	Actual/365
4	European 30/360

Important: 

• Dates should be entered by using the DATE function, or as results of other formulas or functions. For example, use DATE(2018,5,23) for the 23rd day of May, 2018. Problems can occur if dates are entered as text.

• The YEARFRAC function may return an incorrect result when using the US (NASD) 30/360 basis, and the start_date is the last day in February.

Remarks

• Excel stores dates as sequential serial numbers so they can be used in calculations. By default, January 1, 1900 is serial number 1, and January 1, 2018 is serial number 43101 because it is 43,101 days after January 1, 1900.

• All arguments are truncated to integers.

• If start_date or end_date are not valid dates, YEARFRAC returns the #VALUE! error value.

• If basis < 0 or if basis > 4, YEARFRAC returns the #NUM! error value.

Example

Copy the example data in the following table, and paste it in cell A1 of a new Excel worksheet. For formulas to show results, select them, press F2, and then press Enter. If you need to, you can adjust the column widths to see all the data.

Data	Description
1/1/2012	Start date
7/30/2012	End date
Formula	Description	Result
=YEARFRAC(A2,A3)	Fraction of the year between 1/1/2012 and 7/30/12, omitting the Basis argument.	0.58055556
=YEARFRAC(A2,A3,1)	Fraction between same dates, using the Actual/Actual basis argument. Because 2012 is a Leap year, it has a 366 day basis.	0.57650273
=YEARFRAC(A2,A3,3)	Fraction between same dates, using the Actual/365 basis argument. Uses a 365 day basis.	0.57808219

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