CSS: How Large is a CSS Pixel?

By Xah Lee. Date: . Last updated: .

CSS: How Large is a CSS Pixel?

px, in practice, is 1/16 of default font size of a device.

px is defined as reference pixel, which is a visual angle of 0.0213 degrees. This means, the larger the screen, the larger is 1px.

px originally was the same size as a physical pixel of desktop displays in the 1990s.

css reference pixel
CSS Reference Pixel

CSS Spec on What is a Pixel

css spec reference pixel txy3J
Cascading Style Sheets Level 2 Revision 1 (CSS 2.1) Specification, Section 4.3.2 Lengths

CSS Basics

JavaScript in Depth