tan()

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 tan() CSS function is a trigonometric function that returns the tangent of a number, which is a value between −infinity and infinity. The function contains a single calculation that must resolve to either a <number> or an <angle> by interpreting the result of the argument as radians.

Syntax

/* Single <angle> values */
width: calc(100px * tan(45deg));
width: calc(100px * tan(0.125turn));
width: calc(100px * tan(0.785398163rad));

/* Single <number> values */
width: calc(100px * tan(0.5773502));
width: calc(100px * tan(1.732 - 1));

/* Other values */
width: calc(100px * tan(pi / 3));
width: calc(100px * tan(e));

Parameters

The tan(angle) function accepts only one value as its parameter.

angle: A calculation which resolves to a <number> or an <angle>. When specifying unitless numbers they are interpreted as a number of radians, representing an <angle>.

Return value

The tangent of an angle will always return a number between −∞ and +∞.

If angle is infinity, -infinity, or NaN, the result is NaN.
If angle is 0⁻, the result is 0⁻.
If angle is one of the asymptote values (such as 90deg, 270deg, etc.), the result is explicitly undefined. Authors must not rely on tan() returning any particular value for these inputs.

Formal syntax

<tan()> = 
  tan( <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

Drawing parallelograms

The tan() function can be used to draw a parallelogram with a given bounding box.

HTML

<div class="parallelogram"></div>

CSS

.parallelogram {
  --w: 400;
  --h: 200;
  --angle: 30deg;
  position: relative;
  width: calc(1px * var(--w));
  height: calc(1px * var(--h));
}
.parallelogram::before {
  content: "";
  position: absolute;
  width: calc(100% - 100% * var(--h) / var(--w) * tan(var(--angle)));
  height: 100%;
  transform-origin: 0 100%;
  transform: skewX(calc(0deg - var(--angle)));
  background-color: red;
}

Result

Specifications

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

Browser compatibility

	Desktop					Mobile
	Chrome	Edge	Firefox	Opera	Safari	Chrome Android	Firefox for Android	Opera Android	Safari on IOS	Samsung Internet	WebView Android
`tan`	111	111	108	97	15.4	111	108	75	15.4	22.0	111