abs() CSS function

The abs() CSS function returns the absolute value of the argument, as the same type as the input.

Syntax

css
/* abs( <calc-sum> ) */
abs(20% - 100px)
abs(var(--gradientAngle))

Parameters

The abs() function accepts one parameter.

<calc-sum>

An expression or calculation that resolves to a <number>, a <dimension>, a <percentage> or a <calc-keyword>.

Return value

The absolute value of <calc-sum>.

Formal syntax

<abs()> = 
  abs( <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

undefined

Positive variables

The abs() function can be used to ensure that a value is always positive. In the following example a CSS custom property --font-size is used as the value of font-size. Wrapping this custom property in abs() will convert a negative value to a positive one.

css
h1 {
  font-size: abs(var(--font-size));
}

Control gradient angle of direction

You can also control the gradient direction using abs() function. In the following example, with an angle of -45deg the gradient would start red and transition to blue. By using abs() to make the value positive, the gradient will start blue and transition to red.

css
div {
  --deg: -45deg;
  background-image: linear-gradient(abs(var(--deg)), blue, red);
}

Backwards compatible fallback

In browsers that lack support for CSS abs() function, you can use the CSS max() function to achieve the same result:

css
p {
  line-height: max(var(--lh), -1 * var(--lh));
}

We use the max() function to return the largest (most positive) value from a list of two values: var(--lh) or -1 * var(--lh). Irrespective of whether --lh is positive or negative, the calculated return value will always be positive, that is, an absolute number.

Specifications

See also