atan2()

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 atan2() CSS function is a trigonometric function that returns the inverse tangent of two values between -infinity and infinity. The function accepts two arguments and returns the number of radians representing an <angle> between -180deg and 180deg.

Syntax

css
/* Two <number> values */
transform: rotate(atan2(3, 2));

/* Two <dimension> values */
transform: rotate(atan2(1rem, -0.5rem));

/* Two <percentage> values */
transform: rotate(atan2(20%, -30%));

/* Other values */
transform: rotate(atan2(pi, 45));
transform: rotate(atan2(e, 30));

Parameters

The atan2(y, x) function accepts two comma-separated values as its parameters. Each value can be a <number>, a <dimension>, or a <percentage>. Both values must be of the same type, although if they are <dimension> they can be of different units (example: atan2(100px, 5vw) is valid).

y

The y-coordinate of the point. A calculation which resolves to a <number>, a <dimension>, or a <percentage>.

x

The x-coordinate of the point. A calculation which resolves to a <number>, a <dimension>, or a <percentage>.

Return value

Given two values x and y, the function atan2(y, x) calculates and returns the <angle> between the positive x-axis and the ray from the origin to the point (x, y).

Formal syntax

<atan2()> = 
  atan2( <calc-sum> , <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 atan2() 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(atan2(3, 2));
}
div.box-2 {
  transform: rotate(atan2(3%, -2%));
}
div.box-3 {
  transform: rotate(atan2(-1, 0.5));
}
div.box-4 {
  transform: rotate(atan2(1, 0.5));
}
div.box-5 {
  transform: rotate(atan2(1rem, -0.5rem));
}

Result

Specifications

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

Browser compatibility

BCD tables only load in the browser

See also