Screen PPI Calculator
Calculate a display’s pixels per inch, total megapixels and dot pitch from its resolution and diagonal size.
How it works
PPI = √(width² + height²) ÷ diagonal inches
Pixels per inch measures how tightly a panel packs its pixels: the pixel count along the diagonal (by the Pythagorean theorem) divided by the physical diagonal. Dot pitch is the same idea flipped — millimeters per pixel (25.4 ÷ PPI). Higher PPI means sharper text at the same viewing distance, but what matters in practice is PPI relative to how far away you sit: a phone needs far more than a TV.
Worked example
A 27-inch 1920×1080 monitor: diagonal pixels = √(1920² + 1080²) = 2,203, so PPI = 2,203 ÷ 27 = 81.6 — with a 0.311 mm dot pitch and 2.07 megapixels. The same panel at 2560×1440 jumps to 108.8 PPI.
Frequently asked questions
What PPI do I need for a desktop monitor?
At arm’s length, 90–110 PPI is serviceable, 110–140 is comfortable and crisp, and above ~180 you’ll want interface scaling to keep text readable. That is why 1080p feels soft at 27 inches (82 PPI) but fine at 22 (100 PPI).
Does PPI assume square pixels?
Yes — like virtually all modern panels. It also assumes the advertised diagonal is the visible area; a marketing diagonal that includes the bezel would inflate the result slightly.
PPI vs DPI — same thing?
Related but different: PPI describes a screen’s pixels; DPI describes printer dots or a mouse sensor. Print needs roughly 300 DPI at reading distance, which is why "retina-class" phone screens sit in the 300–500 PPI range.
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This calculator is for educational purposes. Double-check important results before acting on them.