CSS Units Live Sandbox

Pixel Box (width: 320px)
Locked to exactly 320 physical screen pixels.

Rem Box (width: 20rem)
Calculates to 320px (20 × 16px). Safe for browser text accessibility resizing.

Parent Wrapper (font-size: 24px)

Em Box (width: 10em)
Calculates to 240px (10 × 24px parent size). Spacing scales up with text size.

Viewport Width Box (width: 40vw)
Always spans exactly 40% of the visible window width. Resize the window to watch it scale!