DPI Calculator (Pixel Density)

DPI counts printer dots per inch, while PPI counts image or display pixels per inch. A display pixel is not a printer dot, so the terms are not interchangeable. Despite its page name, this calculator computes display PPI from pixel dimensions and physical diagonal size.

This calculator classifies 200-349 PPI as Retina-class (typical of high-density laptops and tablets) and 350 PPI and up as ultra-high (premium smartphones). Below 120 PPI, individual pixels are visible at normal viewing distance. Apple's original Retina pitch cited about 300 PPI for a phone held 10 to 12 inches away, since the exact threshold depends on how close you hold the device.

Physical size dilutes resolution. A 27-inch 4K (3840 x 2160) panel works out to about 163 PPI, which this calculator categorizes as standard. A 27-inch 1080p (1920 x 1080) panel is roughly 82 PPI, which falls in the low range. The pixel density difference is real, but Windows and macOS scale the interface by default, so the two screens can look similar until you inspect fine text or icons up close.

For an image, calculate effective PPI at the intended print size. A printer's DPI is a separate hardware setting and may be much higher because several ink dots render one image pixel. Required image PPI depends on viewing distance, process, paper, and print provider, so use the provider's specification.

Check the spec sheet or the model number, for example a Dell U2723 is 27 inches. You can also measure the visible panel corner to corner with a tape measure, excluding the bezel. Most manufacturers publish the diagonal size on the product page or in the manual.