Grid systems form the foundation of interface design. If you are using a design system, there’s a high likelihood that key design decisions — such as spacing, layout, and typography — are subtly influenced by an underlying grid system. The 4-point grid system is the most widely adopted approach in UI design, with many popular design systems incorporating it or a variant of it. But what makes the 4-point grid so special? Why is it the go-to option?

Proportional scaling

One of the most important rules of modern UI design is to maintain a clear visual hierarchy. To achieve this, spacing units must follow a consistent pattern, typically by scaling the base unit with a fixed proportion. The number 4 is highly divisible, as it divides evenly by 1, 2, and 4, making it easy to scale down. Scaling up results in increments of 4, 8, 12, 16, and so on — large enough to be visually distinct yet still manageable. The 4-point grid, therefore, promotes visually harmonious and balanced interfaces.

Micro and macro elements

The 4-point grid hits the sweet spot: it’s not too small to go unnoticed, nor is it too large. For example, 2-point increments might feel too fine, while 6-point or 8-point increments can feel like too large a change. The 4-point increment is precise enough for micro elements, like icons and text padding, while also scaling well for macro elements, such as page margins and grid spacing.

Compatibility and consistency across devices

Different devices have varying screen resolutions and pixel densities. A high-density display packs more pixels than a low-density display. To keep UI elements at a consistent physical size, devices scale the interface based on pixel density. For example, an element with a width of 100px on one screen might scale up to 200px on another screen with twice the pixel density. The scalability of the number 4 aids in maintaining interface compatibility and consistency across devices.

Avoid fractional pixels

A pixel is the smallest unit on the screen, and all elements must have sizes that are whole numbers. The same applies to the spacing and distance between elements. Devices cannot render fractional pixels properly, which can result in blurred or misaligned visuals. Therefore, the interface should scale and maintain all sizes and spacing as whole numbers. This is made easier by the 4-point grid system.

While there are several benefits associated with using the 4-point grid system, it may not always be the best choice for interface design. The 2-point grid system allows for precise and detailed control over UI elements, while the 5-point grid system can provide a unique and unconventional look and feel. Ultimately, the choice of the base grid system for UI design depends on the specific needs and use cases of the product.

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Why the 4-point grid system dominates UI design was originally published in UX Planet on Medium, where people are continuing the conversation by highlighting and responding to this story.