CSS Units – Explained with Examples

CSS units are standardized measurements used in Cascading Style Sheets (CSS) to define various properties such as length, size, and spacing within a web page. These units play a crucial role in determining the layout, dimensions, and appearance of elements on a website. CSS units can be broadly categorized into two main types:

  • Absolute units
  • Relative units

In the below PDF we discuss about  CSS Units in detail in simple language, Hope this will help in better understanding.


Absolute Units:

Absolute units in Cascading Style Sheets (CSS) are a category of length units that provide fixed and unchanging measurements regardless of the context or environment. Unlike relative units, which adapt to their surroundings, absolute units maintain a constant size, making them useful in scenarios where precision and a standardized scale are essential.

Here are some common Absolute units in CSS:

1.  Pixels (px):

  • Represents a single dot on a screen.
  • Provides a fixed-size unit for precise measurements.
  • Commonly used for maintaining consistency across different devices.
.element {
width: 200px;
height: 150px;

2. Inches (in), Centimeters (cm), Millimeters (mm):

  • Absolute physical units.
  • Not commonly used in web design due to their lack of flexibility in responsive layouts.
.element {
width: 2in;
height: 3cm;

3. Points (pt) and Picas (pc):

  • Typically used for print styles.
  • One point is equal to 1/72 of an inch, and one pica is equal to 12 points.
.element {

font-size: 12pt;

line-height: 1.5pc;


Relative Units:

Relative units in CSS are measurements that are defined in relation to other elements or properties within a web page. Unlike absolute units, which have fixed and unchanging values, relative units adapt and scale based on the context in which they are used. These units are crucial for creating flexible, responsive, and proportionate designs that can accommodate various screen sizes and devices.

Here are some common Relative units in CSS:

1.  Percentage (%):

  • Relative to the size of the parent element.
  • Useful for creating fluid layouts that adapt to different screen sizes.
.parent {
width: 80%;

.child {
width: 50%;

2. Viewport Width (vw) and Viewport Height (vh):

  • Relative to the size of the browser window.
  • Facilitates responsive design by adjusting to the viewport dimensions.
.element {
width: 50vw;
height: 75vh;

3. Font-relative Units (em and rem):

Relative to the font-size of the element.
em is relative to its closest parent’s font-size, while rem is relative to the root (usually <html>).

.parent {
font-size: 16px;

.child {
font-size: 1.5em; /* 24px */

.grandchild {
font-size: 1.5rem; /* 16px */


4. Character Units (ch) and X-Height Units (ex):
ch is the width of the zero character.
ex is the height of the lowercase ‘x’.
Useful when working with text to ensure consistent spacing relative to the font.

.element {
width: 20ch;
height: 2ex;

Related Question

A CSS counter is a mechanism that allows you to create and increment/decrement a numerical value in CSS. It is often used in conjunction with the counter-reset and counter-increment properties.

You can define a counter using the counter-reset property.

Yes, counters can be used for nested elements. When defining a counter, it is scoped to the element where it’s defined and its descendants. This allows for counting within specific sections of a document.

Yes, CSS counters are well-supported in modern browsers. However, it’s always a good practice to check browser compatibility for specific features or properties.


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