em scales dynamically with parent elements, making it ideal for fluid and accessible designs.
Key Takeaways:
px is an absolute unit of measurement that defines fixed size while em is a relative unit of measurement in CSS that scales based on its parent element
Using em ensures accessibility and responsiveness by adapting to user preferences and device settings.
px is ideal for fixed layouts, but it may not provide flexibility across devices and screen sizes.
When working with CSS, you might have to choose between using em and px for font sizes, layout dimensions, or length units. This choice impacts the scalability, responsiveness, and maintainability of a website. In this answer, we will discuss each of these units below.
px unit in CSS?The px (pixels) unit is an absolute unit of measurement in CSS. It defines a fixed size, making it consistent across all devices and browsers. With px unit 1px corresponds to one dot on the screen. The px unit can be used for fixed layouts where pixel-perfect precision is required. It can also be used in design mockups or UI elements like buttons and icons.
Here is an example of using the px unit.
In the example above, the h1 element has a fixed size of 24px and the p tag has a fixed size of 16px. No scaling occurs in the h1 and p elements because their font sizes are explicitly defined in pixels (24px and 16px, respectively). These fixed sizes remain constant regardless of the body font size or the device being used to view the content.
Practice using the em unit by trying out this project, Build a Custom Form Maker with MERN Stack, where we create a full stack image sharing application focusing on styling the application.
em unit in CSS?The em unit is a relative unit of measurement in CSS that scales based on its parent element. If the parent element has a font size of 16px, 1em equals 16px. The em unit can be used for fluid, responsive typography and when prioritizing accessibility and user settings.
Here is an example of using the em unit.
In the example above, the h1 size is 2em, so it becomes 40px (2 × 20px base). The .desc class text becomes 12px (60% of 20px base size).
Want to get hands-on practice with using em unit in a real-world application? Try out this project, Build a Microblogging App Using PHP, HTML, JavaScript, and CSS, where we create a microblogging platform with search and admin features.
px with emHere’s a table outlining the key differences between px and em units in CSS:
Feature |
|
|
Unit Type | Absolute unit | Relative unit |
Definition |
|
|
Responsiveness | Less responsive; maintains the same size across different devices and settings. | Highly responsive; adjusts to different screen sizes and user preferences. |
Use Cases | Best for fixed-size elements like borders, icons, and images where precise sizing is needed. | Ideal for typography, spacing, and elements that should adapt to font size change |
Choosing between em and px depends on the specific needs of your application. em units offer flexibility and scalability, making them suitable for responsive designs and improving accessibility. On the other hand, px units provide precision and consistency, which are essential for fixed-layout components. Often, a combination of both units is used to achieve a balanced and adaptable design.
Haven’t found what you were looking for? Contact Us
Free Resources