Author: Oscar Cronquist Article last updated on May 04, 2022

The ACOS function calculates the arccosine, or inverse cosine, of a number.

Formula in cell C3:


Excel Function Syntax



number Required. A number equal to or larger than -1 or equal to or less than 1. -1 <= number <= 1.


The arccosine is the angle whose cosine is number. The returned angle is given in radians in the range 0 (zero) to pi.