PX to EM/REM Converter

Understanding CSS Units: PX, EM, and REM

CSS offers several units for sizing elements, with pixels (px), em, and rem being the most commonly used. Pixels provide absolute sizing, while em and rem offer relative sizing that scales based on font size. Understanding when to use each unit is essential for creating responsive, accessible websites that work well across different devices and user preferences.

The em unit is relative to the font size of the parent element, making it useful for creating scalable components that maintain proportional relationships. However, em values can compound when nested, sometimes leading to unexpected sizes. The rem unit solves this problem by always being relative to the root html element's font size, providing more predictable scaling.

Using relative units like em and rem instead of fixed pixel values makes your website more accessible. When users adjust their browser's default font size, content sized with relative units will scale appropriately, improving readability for users with visual impairments. Modern responsive design best practices recommend using rem for most sizing needs.

The converter below helps you quickly convert between these units. Simply enter a pixel value and your base font size to see the equivalent em and rem values. Most browsers use a default font size of 16px, but always consider that users may change this setting.