lch()

Below are descriptions of the allowed values for both absolute and relative colors.

Absolute value syntax

lch(L C H[ / A])

The parameters are as follows:

L

A <number> between 0 and 100, a <percentage> between 0% and 100%, or the keyword none (equivalent to 0%). The number 0 corresponds to 0% (black), and the number 100 corresponds to 100% (white). This value specifies the color's brightness in the CIELab color space.

Note: The L in lch() is the perceived lightness, which refers to the "brightness" we visually perceive with our eyes. This is different from the L in hsl(), where it represents lightness as compared to other colors.

C

A <number>, a <percentage>, or the keyword none (equivalent to 0% in this case). This value is a measure of the color's chroma (roughly representing the "amount of color"). Its minimum useful value is 0%, or 0, while its maximum is theoretically unbounded (but in practice does not exceed 230), with 100% being equivalent to 150.

H

A <number>, an <angle>, or the keyword none (equivalent to 0deg) representing the color's <hue> angle.

Note: The angles corresponding to particular hues differ across the sRGB (used by hsl() and hwb()), CIELAB (used by lch()), and Oklab (used by oklch()) color spaces. See the hues in LCH example below and the <hue> reference page for more detail and examples.

A Optional

An <alpha-value> representing the alpha channel value of the color, where the number 0 corresponds to 0% (fully transparent) and 1 corresponds to 100% (fully opaque). Additionally, the keyword none can be used to explicitly specify no alpha channel. If the A channel value is not explicitly specified, it defaults to 100%. If included, the value is preceded by a slash (/).

Relative value syntax

lch(from <color> L C H[ / A])

The parameters are as follows:

from <color>

The keyword from is always included when defining a relative color, followed by a <color> value representing the origin color. This is the original color that the relative color is based on. The origin color can be any valid <color> syntax, including another relative color.

L

A <number> between 0 and 100, a <percentage> between 0% and 100%, or the keyword none (equivalent to 0%). The number 0 corresponds to 0% (black), and the number 100 corresponds to 100% (white). This value specifies the color's brightness in the CIELab color space.

C

A <number>, a <percentage>, or the keyword none (equivalent to 0% in this case). This value represents the output color's chroma value (roughly representing the "amount of color"). Its minimum useful value is 0%, or 0, while its maximum is theoretically unbounded (but in practice does not exceed 230), with 100% being equivalent to 150.

H

A <number>, an <angle>, or the keyword none (equivalent to 0deg) representing the output color's <hue> angle. See the hue example below.

A Optional

An <alpha-value> representing the alpha channel value of the output color, where the number 0 corresponds to 0% (fully transparent) and 1 corresponds to 100% (fully opaque). Additionally, the keyword none can be used to explicitly specify no alpha channel. If the A channel value is not explicitly specified, it defaults to the alpha channel value of the origin color. If included, the value is preceded by a slash (/).

Defining relative color output channel components

When using relative color syntax inside an lch() function, the browser converts the origin color into an equivalent Lch color (if it is not already specified as such) The color is defined as three distinct color channel values — l (lightness), c (chroma), and h (hue) — plus an alpha channel value (alpha). These channel values are made available inside the function to be used when defining the output color channel values:

• The l channel value is resolved to a <number> between 0 and 100, inclusive.
• The c channel value is resolved to a <number> between 0 and 150, inclusive.
• The h channel value is resolved to a <number> between 0 and 360, inclusive.
• The alpha channel is resolved to a <number> between 0 and 1, inclusive.

When defining a relative color, the different channels of the output color can be expressed in several different ways. Below, we'll study some examples to illustrate these.

In the first two examples below, we are using relative color syntax. However, the first one outputs the same color as the origin color and the second one outputs a color not based on the origin color at all. They don't really create relative colors! You'd be unlikely to ever use these in a real codebase, and would probably just use an absolute color value instead. We included these examples as a starting point for learning about relative lch() syntax.

Let's start with an origin color of hsl(0 100% 50%) (equivalent to red). The following function outputs the same color as the origin color — it uses the origin color's l, c, and h channel values (54.29, 106.854, and 40.856) as the output channel values:

lch(from hsl(0 100% 50%) l c h)

This function's output color is lch(54.29 106.854 40.856).

The next function uses absolute values for the output color's channel values, outputting a completely different color not based on the origin color:

lch(from hsl(0 100% 50%) 29.6871% 66.83 327.109)

In the above case, the output color is lch(29.6871 66.83 327.109).

The following function creates a relative color based on the origin color:

lch(from hsl(0 100% 50%) 70 150 h)

This example:

• Converts the hsl() origin color to an equivalent lch() color — lch(54.29 106.854 40.856).
• Sets the H channel value for the output color to that of the origin lch() equivalent's H channel value — 40.856.
• Sets the output color's L and C channel values to new values not based on the origin color: 70 and 150 respectively.

The final output color is lch(70 150 40.856).

In the examples we've seen so far in this section, the alpha channels have not been explicitly specified for either the origin or output colors. When the output color alpha channel is not specified, it defaults to the same value as the origin color alpha channel. When the origin color alpha channel is not specified (and it is not a relative color), it defaults to 1. Therefore, the origin and output alpha channel values are 1 for the above examples.

Let's look at some examples that specify origin and output alpha channel values. The first one specifies the output alpha channel value as being the same as the origin alpha channel value, whereas the second one specifies a different output alpha channel value, unrelated to the origin alpha channel value.

lch(from hsl(0 100% 50% / 0.8) l c h / alpha)
/* Computed output color: lch(54.29 106.854 40.856 / 0.8) */

lch(from hsl(0 100% 50% / 0.8) l c h / 0.5)
/* Computed output color: lch(54.29 106.854 40.856 / 0.5) */

In the following example, the hsl() origin color is again converted to the lch() equivalent — lch(54.29 106.854 40.856). calc() calculations are applied to the L, C, H, and A values, resulting in an output color of lch(74.29 86.8541 0.856018 / 0.9):

lch(from hsl(0 100% 50%) calc(l   20) calc(c - 20) calc(h - 40) / calc(alpha - 0.1))

<lch()> = 
  lch( [ <percentage> | <number> | none ] [ <percentage> | <number> | none ] [ <hue> | none ] [ / [ <alpha-value> | none ] ]? )  

<hue> = 
  <number>  |
  <angle>   

<alpha-value> = 
  <number>      |
  <percentage>  

This example shows the effect of varying the L (lightness) value of the lch() functional notation.

HTML

<div data-color="blue-dark"></div>
<div data-color="blue"></div>
<div data-color="blue-light"></div>

<div data-color="red-dark"></div>
<div data-color="red"></div>
<div data-color="red-light"></div>

<div data-color="green-dark"></div>
<div data-color="green"></div>
<div data-color="green-light"></div>

CSS

body {
  display: grid;
  grid-template-columns: 1fr 1fr 1fr;
  gap: 20px;
}
div {
  height: 50px;
  border: 1px solid black;
}

[data-color="blue-dark"] {
  background-color: lch(10% 100 240);
}
[data-color="blue"] {
  background-color: lch(50% 100 240);
}
[data-color="blue-light"] {
  background-color: lch(90% 100 240);
}

[data-color="red-dark"] {
  background-color: lch(10% 130 20);
}
[data-color="red"] {
  background-color: lch(50% 130 20);
}
[data-color="red-light"] {
  background-color: lch(90% 130 20);
}

[data-color="green-dark"] {
  background-color: lch(10% 132 130);
}
[data-color="green"] {
  background-color: lch(50% 132 130);
}
[data-color="green-light"] {
  background-color: lch(90% 132 130);
}

Result

The following example shows the effect of varying the C (chroma) value of the lch() functional notation, with colors decreasing in intensity as the C value decreases from fully saturated to almost grey.

HTML

<div data-color="blue"></div>
<div data-color="blue-chroma1"></div>
<div data-color="blue-chroma2"></div>
<div data-color="blue-chroma3"></div>

<div data-color="red"></div>
<div data-color="red-chroma1"></div>
<div data-color="red-chroma2"></div>
<div data-color="red-chroma3"></div>

<div data-color="green"></div>
<div data-color="green-chroma1"></div>
<div data-color="green-chroma2"></div>
<div data-color="green-chroma3"></div>

CSS

With the initial starting colors blue, red, and green, we declare progressively smaller values for chroma on them: starting from full color saturation at the highest value of 150 (equivalent to 100%) down to 3 (equivalent to 2%), which is almost grey for all the colors.

body {
  display: grid;
  grid-template-columns: 1fr 1fr 1fr 1fr;
  gap: 20px;
}
div {
  height: 50px;
  border: 1px solid black;
}

[data-color="blue"] {
  background-color: lch(50% 150 240);
}
[data-color="blue-chroma1"] {
  background-color: lch(50% 105 240);
}
[data-color="blue-chroma2"] {
  background-color: lch(50% 54 240);
}
[data-color="blue-chroma3"] {
  background-color: lch(50% 3 240);
}

[data-color="red"] {
  background-color: lch(50% 100% 20deg);
}
[data-color="red-chroma1"] {
  background-color: lch(50% 70% 20deg);
}
[data-color="red-chroma2"] {
  background-color: lch(50% 36% 20deg);
}
[data-color="red-chroma3"] {
  background-color: lch(50% 2% 20deg);
}

[data-color="green"] {
  background-color: lch(50% 150 130);
}
[data-color="green-chroma1"] {
  background-color: lch(50% 105 130);
}
[data-color="green-chroma2"] {
  background-color: lch(50% 54 130);
}
[data-color="green-chroma3"] {
  background-color: lch(50% 3 130);
}

Result

If we had used 0 instead of 3 and 2%, with the same lightness values, the colors would have all been the same shade of grey. In this example, they are almost grey.

The following example shows swatches with different H (hue) values of the lch() functional notation.

HTML

<div data-color="0">0deg</div>
<div data-color="20">20deg</div>
<div data-color="40">40deg</div>
<div data-color="60">60deg</div>

and so on.

<div data-color="80">80deg</div>
<div data-color="100">100deg</div>
<div data-color="120">120deg</div>
<div data-color="140">140deg</div>
<div data-color="160">160deg</div>
<div data-color="180">180deg</div>
<div data-color="200">200deg</div>
<div data-color="220">220deg</div>
<div data-color="240">240deg</div>
<div data-color="260">260deg</div>
<div data-color="280">280deg</div>
<div data-color="300">300deg</div>
<div data-color="320">320deg</div>
<div data-color="340">340deg</div>
<div data-color="360">360deg</div>

CSS

body {
  display: flex;
  flex-wrap: wrap;
  gap: 3px;
}
div {
  flex: 0 0 4em;
  text-align: center;
  line-height: 4em;
  display: inline-block;
  border: 1px solid black;
  color: white;
  font-family: monospace;
}

[data-color="0"] {
  background-color: lch(50% 150 0deg);
}
[data-color="20"] {
  background-color: lch(50% 150 20deg);
}
[data-color="40"] {
  background-color: lch(50% 150 40deg);
}
[data-color="60"] {
  background-color: lch(50% 150 60deg);
}

and so on.

[data-color="80"] {
  background-color: lch(50% 150 80deg);
}
[data-color="100"] {
  background-color: lch(50% 150 100deg);
}
[data-color="120"] {
  background-color: lch(50% 150 120deg);
}
[data-color="140"] {
  background-color: lch(50% 150 140deg);
}
[data-color="160"] {
  background-color: lch(50% 150 160deg);
}
[data-color="180"] {
  background-color: lch(50% 150 180deg);
}
[data-color="200"] {
  background-color: lch(50% 150 200deg);
}
[data-color="220"] {
  background-color: lch(50% 150 220deg);
}
[data-color="240"] {
  background-color: lch(50% 150 240deg);
}
[data-color="260"] {
  background-color: lch(50% 150 260deg);
}
[data-color="280"] {
  background-color: lch(50% 150 280deg);
}
[data-color="300"] {
  background-color: lch(50% 150 300deg);
}
[data-color="320"] {
  background-color: lch(50% 150 320deg);
}
[data-color="340"] {
  background-color: lch(50% 150 340deg);
}
[data-color="360"] {
  background-color: lch(50% 150 360deg);
}

Result

The hue angles in lch() are different from those in hsl(). See <hue> for more information. In hsl(), the sRGB color 0deg represents red. However, in the CIELab color space, 0deg corresponds to magenta, while red is approximately 41deg.

The following example shows the effect of varying the A (alpha) value of the lch() functional notation. The red and red-alpha elements overlap the #background-div element to demonstrate the effect of opacity. Giving A a value of 0.4 makes the color 40% opaque.

HTML

<div id="background-div">
  <div data-color="red"></div>
  <div data-color="red-alpha"></div>
</div>

CSS

div {
  width: 50px;
  height: 50px;
  padding: 5px;
  margin: 5px;
  display: inline-block;
  border: 1px solid black;
}
#background-div {
  background-color: lch(100% 100 240);
  width: 150px;
  height: 40px;
}

[data-color="red"] {
  background-color: lch(50% 130 20);
}
[data-color="red-alpha"] {
  background-color: lch(50% 130 20 / 0.4);
}

Result

This example styles three <div> elements with different background colors, demonstrating the use of relative colors to change a color's brightness using the lch() color function. The middle <div> retains the original --base-color, while the left and right <div>s are given lightened and darkened variants of the --base-color.

These variants are defined using relative colors — the --base-color custom property is passed into an lch() function, and the output colors have their lightness channel modified to achieve the desired effect via a calc() function. The lightened color has 15% added to the lightness channel, and the darkened color has 15% subtracted from the lightness channel.

<div id="container">
  <div class="item" id="one"></div>
  <div class="item" id="two"></div>
  <div class="item" id="three"></div>
</div>

CSS

#container {
  display: flex;
  width: 100vw;
  height: 100vh;
  box-sizing: border-box;
}

.item {
  flex: 1;
  margin: 20px;
}

:root {
  --base-color: orange;
}

#one {
  background-color: lch(from var(--base-color) calc(l   15) c h);
}

#two {
  background-color: var(--base-color);
}

#three {
  background-color: lch(from var(--base-color) calc(l - 15) c h);
}

Result

The output is as follows:

• List of all color notations
• Using relative colors
• CSS colors module
• <hue> data type
• LCH colors in CSS: what, why, and how? by Lea Verou (2020)