Responsive web design demands fluid typography and spacing. However, many developers still rely entirely on absolute units like pixels (px), which breaks accessibility for users who scale their browser's default font size.
Absolute vs. Relative Units
Pixels (px) are absolute. If you set a font size to 16px, it stays 16px regardless of the user's OS accessibility settings. This is poor practice for typography.
REM (Root EM) is relative to the root <html> font size. If the user's browser is set to 16px, 1rem equals 16px. If they need larger text and set it to 24px, 1rem scales to 24px automatically. To ensure accessible layouts, use our PX to REM Converter.
When to Use EM
The EM unit is relative to its direct parent element. This makes it incredibly powerful for modular components (like buttons) where the padding should scale proportionally to the component's font size. Test these relationships using our PX to EM Tool.
Viewport Units
For layout constraints, viewport units (vw, vh) map to the percentage of the browser window. They are essential for full-screen hero sections. Translate your Figma designs accurately using the PX to VH Calculator.