Pixel density tells you how sharp a screen looks or how high a resolution an image needs to be for a given print size. The two standard measures are PPI (pixels per inch) for screens and DPI (dots per inch) for print output, though the terms are often used interchangeably in everyday conversation. For screens, a higher PPI means individual pixels are harder to see from normal viewing distance, producing a sharper image. A standard desktop monitor is typically 90 to 110 PPI, a high-definition laptop display sits around 150 to 200 PPI, and a phone screen may exceed 400 PPI. For print, 300 DPI is the standard for photographic quality output, while 150 DPI is acceptable for documents viewed from reading distance and 72 DPI is sufficient for screen-only images. This calculator works in two modes. Screen PPI mode takes the horizontal and vertical pixel count of the screen and the diagonal screen size in inches, and returns the PPI, dot pitch in millimetres, and the diagonal pixel count. Print DPI mode takes the desired output DPI and the print width and height in inches, and returns the pixel dimensions required. You switch between modes using the selector below. The default is screen PPI mode with a 1920 by 1080 resolution on a 24-inch diagonal, which represents a typical desktop monitor.
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91.79 PPI
screen pixel density
Dot pitch0.277 mm
Diagonal pixels2,203 px
Total pixels2,073,600 px
How it works
For screen PPI: diagonal pixel count = sqrt(W² + H²) where W and H are horizontal and vertical pixel counts. PPI = diagonal pixel count divided by diagonal screen size in inches. Dot pitch in mm = 25.4 divided by PPI. Total pixels = W times H. For print DPI: required pixel width = print width (in) times DPI; required pixel height = print height (in) times DPI. Total pixels = width times height.
Worked example
Screen mode: a monitor has a resolution of 1920 times 1080 pixels on a 24-inch diagonal. Diagonal pixels = sqrt(1920² + 1080²) = sqrt(3,686,400 + 1,166,400) = sqrt(4,852,800) = 2,202.9 pixels. PPI = 2202.9 divided by 24 = 91.79 PPI. Dot pitch = 25.4 / 91.79 = 0.277 mm. Total pixels = 1920 times 1080 = 2,073,600. For the print mode: 300 DPI on a 4 by 6 inch print requires 4 times 300 = 1200 px wide and 6 times 300 = 1,800 px tall.
