Convert Dots per pixel to Dots per centimetre

Convert Dots per pixel (dppx) to Dots per centimetre (dpcm) instantly and accurately.

Conversion Formula

dpcm = dppx × 37.79527559

About Dots per pixel

The dot per CSS-pixel unit (dppx, or the x descriptor in CSS) is defined in W3C CSS Images Level 3 / Media Queries Level 4 as the ratio of physical device pixels to CSS reference pixels, where the CSS spec fixes 1 CSS inch ≡ 96 CSS px exactly. Therefore 1 dppx = 96 DPI = 96 PPI exactly; a screen reporting device pixel ratio (DPR) of 2 has 2 dppx = 192 physical dots per CSS inch. JavaScript exposes DPR as window.devicePixelRatio, numerically equal to dppx. Reference values: standard laptop (96-110 PPI): 1 dppx; MacBook Pro 13-inch Retina (227 PPI): 2 dppx; iPhone 15 Pro 6.1-inch (460 PPI): 3 dppx; Samsung Galaxy S24 Ultra (501 PPI): ≈ 3.09 dppx. The HTML img srcset x descriptor (photo@2x.jpg 2x) is numerically equal to dppx, serving higher-resolution images for HiDPI screens. The CSS @media (min-resolution: 2dppx) query targets any display with DPR ≥ 2. 1 dppx = 96 DPI = 96 PPI.

About Dots per centimetre

The dot per centimetre (dpcm) is the metric equivalent of DPI, defined as a CSS resolution unit in the W3C CSS Images Level 3 specification alongside dpi and dppx. A 96 DPI reference screen (CSS Media Queries Level 4 reference device) corresponds to 96/2.54 ≈ 37.795 dpcm. ITU-T T.4 (Group 3 facsimile, 1980) defines scan line density in metric units: standard resolution 3.85 lines/mm = 38.5 dpcm; fine resolution 7.7 lines/mm = 77 dpcm. ITU-T T.85 (JBIG compression) standardised these metric resolutions for cross-border interoperability. ISO 216 A4 scanned at 77 dpcm fine fax resolution yields 1617 pixels across page width. The CSS specification recommends dppx over dpcm for screen media queries, reserving dpcm for print stylesheets targeting metric-resolution printers. 1 dpcm = 2.54 DPI = 2.54 PPI exactly (since 1 in = 2.54 cm). 1 dpcm = 0.1 dot/mm.

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