Point Size to Pixel Conversion Calculator

A point is a physical unit of length, and in all modern software it equals exactly 1/72 of an inch, so 72pt is one inch and 12 points make one pica. A pixel is a device unit whose physical size depends on the display, so converting between them requires a resolution figure: pixels equal points multiplied by DPI divided by 72. At the CSS reference resolution of 96 DPI this reduces to a factor of 4/3, which is why 12pt maps to 16px, 9pt to 12px and 18pt to 24px. Print work uses 300 DPI for offset-quality raster output, making 12pt equal 50 pixels, while legacy Macintosh displays at 72 DPI made a point and a pixel identical. The critical subtlety is that the CSS pixel is not a hardware pixel. CSS defines an absolute anchoring where 1 inch equals exactly 96 pixels, treating the pixel as a reference unit scaled for viewing distance rather than a physical dot; hardware density is exposed separately through devicePixelRatio, so a modern phone may render one CSS pixel across three device pixels. Two further caveats matter. Historical point systems were not 1/72 inch: the Didot point used across continental Europe measures about 0.3759mm and the American printers point standardised in the 1880s measures 0.013837 inch, both slightly larger than the modern value, so type specified from older specimen books will not match exactly. And point size describes the em square, not any visible dimension of the letters, so two faces set at the same point size can differ markedly in apparent size because their x-heights differ.

Type was sized by named bodies such as pica, brevier and nonpareil until Pierre Simon Fournier proposed a numerical point system in Paris around 1737, dividing the French inch into a fixed number of equal points so that sizes could be specified arithmetically and mixed on the same line. Francois-Ambroise Didot revised the system in about 1783, re-anchoring it to the official pied du roi and producing the Didot point of roughly 0.3759mm, which became the standard across most of continental Europe and survived into the twentieth century. The English-speaking trade converged separately. In 1886 the United States Type Founders Association adopted the Johnson pica of the MacKellar, Smiths and Jordan foundry as its standard, giving a point of 0.013837 inch, close to but not exactly 1/72 inch. Digital typesetting simplified the arithmetic: when Adobe introduced PostScript in 1984 and 1985 it defined the point as precisely 1/72 inch, and because the original Apple Macintosh screen of 1984 ran at 72 dots per inch, one point equalled one screen pixel and what appeared on the display matched the printed size. Microsoft Windows instead used a 96 DPI logical inch, which produced the persistent 4:3 discrepancy between the two platforms. The W3C eventually fixed the web on the Windows figure, defining 1 inch as 96 CSS pixels in CSS 2.1 and carrying that anchoring into the CSS Values and Units modules.