Whether you’re speccing a new monitor, designing for a specific pixel density, or just curious what “4K” actually means in numbers, the Screen Resolution Calculator breaks down any resolution into aspect ratio, megapixels, and PPI.
How PPI is calculated
Pixels-per-inch (PPI) measures pixel density — how tightly packed the pixels are on a given screen. It’s calculated by taking the resolution’s diagonal length in pixels (using the Pythagorean theorem on width and height) and dividing by the physical diagonal screen size in inches. This is why a smartphone screen can have a much higher PPI than a large TV running the same resolution — the same number of pixels is packed into a much smaller physical space.
Reducing to a clean aspect ratio
Raw pixel dimensions like 1920×1080 get reduced to their simplest form using the greatest common divisor, producing the familiar 16:9 you see marketed — rather than showing the unreduced numbers, which wouldn’t mean much at a glance.
Recognizing common resolution names
The tool includes a lookup table for widely recognized resolution names — HD, Full HD, QHD/1440p, 4K UHD, 8K UHD, and a few widescreen/ultrawide variants — so you instantly see the marketing name alongside the raw numbers. Less common or custom resolutions simply won’t have a recognized name, which is expected.
Try it yourself
Enter any resolution (and optionally your screen’s diagonal size) on the Screen Resolution Calculator to get instant aspect ratio, megapixel count, and PPI.