Convert Pixels per inch to Pixels per centimetre

Convert Pixels per inch (PPI) to Pixels per centimetre (px/cm) instantly and accurately.

Conversion Formula

px/cm = PPI × 0.3937007874

About Pixels per inch

The pixel per inch (PPI) is the universal standard for digital image resolution, defining how many pixels occupy one linear inch in a digital image, sensor, or display. Formally referenced in ISO 12232 (digital still cameras) and EXIF/TIFF (tags 0x011A/0x011B), PPI is both a capture parameter (scanner/sensor density) and a display characteristic. Display milestones: Macintosh 128K (1984): 72 PPI; Apple iPhone 4 Retina (2010): 326 PPI - above the human perceptual threshold at 25 cm; iPhone 15 Pro (2023): 460 PPI. Print benchmarks: 150 PPI (large-format, 1 m viewing); 300 PPI (standard offset, ISO 12647-2); 400-600 PPI (fine-art Giclée). EXIF stores PPI as unsigned RATIONAL; the historical default is 72/1, a carry-over from the original Macintosh screen standard. 1 PPI = 1/0.0254 px/m ≈ 39.37 px/m = 2.54 px/cm.

About Pixels per centimetre

The pixel per centimetre (px/cm) is the metric counterpart of PPI, measuring pixel density per centimetre. EXIF assigns ResolutionUnit = 3 when resolution is stored in px/cm; Canon, Fujifilm, and Nikon cameras can output EXIF data in px/cm. GIMP stores and displays image resolution in px/cm in its XCF format and Image Properties dialog. DICOM (NEMA PS 3.3) stores spatial resolution as PixelSpacing in mm/pixel; a radiograph at 0.2 mm/px = 5 px/mm = 50 px/cm = 127 PPI. At 10×15 cm print size, a 12 MP image (4000×3000 px) prints at 4000/15 ≈ 266.7 px/cm ≈ 677 PPI - well above the ISO 12647-2 minimum of ≈ 118 px/cm (300 PPI). Since 1 inch = 2.54 cm exactly, 1 px/cm = 2.54 PPI exactly. 1 px/cm = 2.54 PPI = 10 px/dm = 100 px/m.

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