Px vs. Em vs. Rem: Which CSS Unit Should You Use?
When it comes to web development, CSS units play a crucial role in defining the size, spacing, and layout of HTML elements. The commonly used CSS units are pixels (px), ems (em), and rems (rem). Choosing the right unit for your project can make a significant difference in the responsiveness and adaptability of your web pages.
Pixels (px) is perhaps the most popular CSS unit used to define the size of an HTML element. A pixel is a fixed unit that represents the actual pixels on the screen of the device. Pixels are best used when designing graphics or when a specific size is required for an element, such as a logo or header. However, the downsides to using pixels are that they are not flexible and do not scale well. When a user changes the device’s screen size or resolution, the pixel-based elements may appear distorted or disproportionate.
On the other hand, the ’em’ (pronounced as ‘M’) unit is relative to the font size of the parent element. The size of the em unit depends on the font size specified in the parent element. For instance, if the parent element has a font-size of 20px, and we set a child element to have a font-size value of1.5em, the child element’s font size will be 30px. The em unit’s flexibility makes it an ideal option for responsive design because elements’ sizes adjust according to the parent’s font size, regardless of the device.
The ‘rem’ unit is like the ’em’ unit, but relative to the font size of the root element (html or body) rather than the parent element, making it an excellent option for responsive web design. Rem units make it easy to scale elements uniformly across the page since they establish a uniform base from which all children elements derive their measurements. Generally, rem can be used in various aspects, such as font-size, padding, margin, width, height, and so on.