atan()

Baseline 2023

Newly available

Since March 2023, this feature works across the latest devices and browser versions. This feature might not work in older devices or browsers.

The atan() CSS function is a trigonometric function that returns the inverse tangent of a number between -∞ and +∞. The function contains a single calculation that returns the number of radians representing an <angle> between -90deg and 90deg.

Syntax

css
/* Single <number> values */
transform: rotate(atan(1));
transform: rotate(atan(4 * 50));

/* Other values */
transform: rotate(atan(pi / 2));
transform: rotate(atan(e * 3));

Parameters

The atan(number) function accepts only one value as its parameter.

number

A calculation which resolves to a <number> between -∞ and +∞.

Return value

The inverse tangent of an number will always return an <angle> between -90deg and 90deg.

  • If number is 0⁻, the result is 0⁻.
  • If number is +∞ the result is 90deg.
  • If number is -∞ the result is -90deg.

That is:

  • atan(-infinity) representing -90deg.
  • atan(-1) representing -45deg
  • atan(0) representing 0deg
  • atan(1) representing 45deg
  • atan(infinity) representing 90deg.

Formal syntax

<atan()> = 
  atan( <calc-sum> )  

<calc-sum> = 
  <calc-product> [ [ '+' | '-' ] <calc-product> ]*  

<calc-product> = 
  <calc-value> [ [ '*' | '/' ] <calc-value> ]*  

<calc-value> = 
  <number>        |
  <dimension>     |
  <percentage>    |
  <calc-keyword>  |
  ( <calc-sum> )  

<calc-keyword> = 
  e          |
  pi         |
  infinity   |
  -infinity  |
  NaN

Examples

Rotate elements

The atan() function can be used to rotate elements as it return an <angle>.

HTML

html
<div class="box box-1"></div>
<div class="box box-2"></div>
<div class="box box-3"></div>
<div class="box box-4"></div>
<div class="box box-5"></div>

CSS

css
div.box {
  width: 100px;
  height: 100px;
  background: linear-gradient(orange, red);
}
div.box-1 {
  transform: rotate(atan(-99999));
}
div.box-2 {
  transform: rotate(atan(-1));
}
div.box-3 {
  transform: rotate(atan(0));
}
div.box-4 {
  transform: rotate(atan(1));
}
div.box-5 {
  transform: rotate(atan(99999));
}

Result

Specifications

Specification
CSS Values and Units Module Level 4
# trig-funcs

Browser compatibility

BCD tables only load in the browser

See also