PPI Calculator

Pixels Per Inch measures the spatial density of pixels on a display. The calculation uses the Pythagorean theorem to find the diagonal pixel count from the horizontal and vertical resolution, then divides by the physical diagonal size of the screen. PPI is sometimes confused with DPI (dots per inch), but they refer to different things. PPI describes screen displays, while DPI describes print resolution. For digital images displayed on screens, PPI is the relevant metric. Apple popularized the concept of high PPI displays with the Retina display, which exceeds the resolving ability of the human eye at typical viewing distances (approximately 300 PPI for smartphones held at 10-12 inches and 220 PPI for tablets). At these densities, individual pixels become imperceptible. Common PPI values include: standard desktop monitors at 72-110 PPI, high-resolution laptops at 200-230 PPI, smartphones at 300-550 PPI, and professional photo editing monitors at 140-220 PPI. For print design, understanding PPI is crucial because it determines how many pixels of your digital image map to each inch of printed output. A 300 PPI image printed at actual size produces professional-quality output. When comparing displays, PPI is more meaningful than raw resolution because it accounts for screen size. A 4K (3840x2160) display at 27 inches has 163 PPI, while the same resolution at 55 inches yields only 80 PPI.