How it works
Pixel density, in pixels per inch (PPI), is the number of pixels along the diagonal divided by the diagonal length in inches. Higher PPI means sharper text and images at the same viewing distance.
The aspect ratio is the resolution reduced to its simplest form. Some resolutions, like 1366×768, are not exactly 16:9, so the nearest standard ratio is shown as well.
Physical width and height come from the diagonal and the aspect ratio using the Pythagorean theorem. Listed screen sizes are often rounded, so real measurements can differ slightly.
Formula
PPI = √(width² + height²) ÷ diagonal
Questions people ask
What PPI is considered sharp?
At typical desk distance, around 110 PPI looks fine and 140 PPI or more looks crisp. Phones, held closer, usually exceed 400 PPI.
Is PPI the same as DPI?
They are often used interchangeably. Strictly, PPI describes screen pixels and DPI describes printer ink dots.
How wide is a 27-inch 16:9 monitor?
About 23.5 inches (59.8 cm) wide and 13.2 inches (33.6 cm) tall.