Pixel (CSS) (px)

Typography & screenCurrent unit

The CSS reference pixel, defined as 1/96 of an inch. Physical screens vary, but browsers use this value to convert pixels to print units.

1 pixel (CSS) = 0.0002645833333 meters (approximately).

About the pixel (CSS)

Pixel is a contraction of picture element, itself built from pix, a 1930s shortening of pictures. The idea is older than the word: Paul Nipkow's 1888 German patent spoke of a Bildpunkt, or picture point, and the phrase picture element appears in US patents filed as early as 1911. Frederic C. Billingsley of the Jet Propulsion Laboratory published pixel in 1965, writing about scanned images from space probes to the Moon and Mars, and said he had learned it from Keith E. McFarland, who reported it was already in use around 1963.

A pixel in a photograph is a sample, not a fixed length, and screens vary widely in size. CSS therefore defines px as an abstract reference pixel of exactly 1/96 inch, based on the visual angle of one pixel on a 96 dpi device held at arm's length. The CSS specification gives that angle as about 0.0213 degrees for a nominal arm's length of 28 inches, which works out to about 0.26 mm. On sharper screens a single CSS pixel spans several device pixels. Earlier CSS versions did not fix the ratio, but too much existing content assumed 96 dpi.

Sources: W3C: CSS Values and Units Module Level 3, absolute lengths; Wikipedia: Pixel

Pixel (CSS) conversion chart

1 pixel (CSS) expressed in every other length unit:

More Typography & screen units

• point (length)
• pica (length)
• twip (length)

All Typography & screen units

Browse all length units.