ACOS function

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


Returns the arccosine, or inverse cosine, of a number. The arccosine is the angle whose cosine is number. The returned angle is given in radians in the range 0 (zero) to pi.



The ACOS function syntax has the following arguments:

  • Number    Required. The cosine of the angle you want and must be from -1 to 1.


If you want to convert the result from radians to degrees, multiply it by 180/PI() or use the DEGREES function.


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.





Arccosine of -0.5 in radians, 2*pi/3



Arccosine of -0.5 in degrees



Arccosine of -0.5 in degrees


Applies To: Excel Starter, Excel 2016 for Mac, Excel 2010, Excel 2013, Excel 2016, Excel for Mac 2011, Excel Online, Excel 2007

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