`abs()` CSS function

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

Syntax

/* 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>.

• If <calc-sum>'s numeric value is positive or 0⁺, the function returns <calc-sum>.
• Otherwise, it returns -1 * <calc-sum>.

Formal syntax

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

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

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

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

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

Examples

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.

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.

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:

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

Browser compatibility

See also

• sign()