Choosing Font Size Units in Web Design: Pixels vs Rem — What’s the Best Approach?

The world of web design is constantly evolving, but one of the fundamental issues designers and developers face is the choice of font size units.
This article focuses on both traditional design tools such as Photoshop and modern web design tools (Sketch, Figma, Adobe XD, etc.), explaining in detail the characteristics and optimal use cases of “pixels (px)” and “rem” as font size units, as well as points (pt) and their associated issues.

What Are Font Size Units?

Font size units refer to the numerical values used to define the size of text. In web design, they are a crucial element that determines how large text appears on the screen.

Characteristics of Pixels (px)

• Precision:
  Pixels are a fixed-size unit, ensuring that text is displayed exactly at the size intended by the designer.
• Compatibility:
  They are consistently supported across all browsers and are commonly used in design tools such as Photoshop.

Characteristics of Rem

• Independence from parent elements:
  1rem is based on the font size of the root element.
• Suitability for responsive design:
  By changing only the root font size, the text size of the entire site can be adjusted at once.
• Accessibility:
  Text scales appropriately even when users change font size settings in their browser.

Points (pt) and Their Issues

There is also a font size unit called “pt” (points) in web design. However, using pt as a primary unit in web design is not recommended. The reasons are as follows:

• Dependence on resolution:
  Points are a physical unit and depend on screen resolution, so their appearance is not consistent across different devices and resolutions. As a result, the displayed size often differs from what is expected in web design.
• Browser compatibility:
  Points can result in significant differences in appearance between browsers, especially on mobile devices, which can negatively impact user experience.
• Confusion with print design:
  Points are traditionally used in print design. Web design and print design are different media with different requirements and constraints. Using print-oriented units in web design can lead to confusion.

Therefore, in web design, it is recommended to use units suitable for screen displays, such as pixels (px) or rem.

Choosing the Appropriate Unit by Tool

• Photoshop:
  Since it is mainly used for creating static designs, pixels are the most common choice.
• Web design tools (Sketch, Figma, Adobe XD, etc.):
  These tools support real-time previews and component-based design, making it effective to design primarily using rem.

Conclusion: Pixels vs Rem — Which Should You Choose?

The best approach to choosing font size units in web design depends on the tools and objectives of your project. While pixels are the standard in traditional design tools like Photoshop, rem is recommended in modern web design tools and actual web development when considering responsive design and accessibility.

Ultimately, the most important thing is to choose the appropriate font size unit based on the project’s requirements, goals, and the tools and technologies being used.

　
*Please use this information at your own discretion.*