PPI Calculator
See how sharp a screen really is — pixel density in pixels per inch, plus the dot pitch between pixels.
Higher PPI is sharper
The more pixels packed into each inch, the finer the detail and the smoother text and edges appear.
Square pixels assumed
The result assumes square pixels and a flat panel — the standard for almost every modern monitor, laptop, phone, and TV.
What is PPI (pixel density)?
Pixels per inch of screen
PPI — pixels per inch — measures how densely the pixels are packed on a display. Two screens can share the same resolution yet look very different: 1920 × 1080 on a 24-inch monitor spreads those pixels across more space than the same resolution on a 6-inch phone, so the phone looks far crisper. PPI captures that by combining resolution and physical size into a single number, which is why it is the standard way to compare the sharpness of monitors, laptops, phones, and TVs.
Find the diagonal length in pixels with the Pythagorean theorem, then divide by the physical diagonal in inches.
PPI = √(width² + height²) ÷ diagonalThe square root of the squared width plus the squared height gives the diagonal measured in pixels — 2202.9 pixels for 1920 × 1080. Dividing by the 24-inch diagonal yields the pixel density. The dot pitch is simply the inverse, scaled to millimetres: 25.4 ÷ PPI, since one inch is 25.4 mm.
Suppose you have a 24-inch monitor running at 1920 × 1080.
Diagonal in pixels
√(1920² + 1080²) = √(3,686,400 + 1,166,400) = 2202.9 pixels.
Divide by the inches
2202.9 ÷ 24 = 91.8 PPI.
Find the dot pitch
25.4 ÷ 91.8 = 0.2767 mm between pixels.
A typical desktop monitor sits around 90 to 110 PPI, which looks fine at normal viewing distance. Laptops and high-resolution displays climb to 150 PPI and beyond, while modern phones and "Retina"-class screens reach 200 to 500+ PPI, where individual pixels become invisible at arm's length. As a rule, higher PPI means a sharper image — but the comfortable threshold depends on how close you sit, since a TV viewed from across the room needs far less density than a phone held inches from your eyes. The dot pitch is the inverse view of the same fact: a smaller dot pitch means pixels are closer together, so a 0.28 mm pitch is coarser than a 0.10 mm one.
The formula is exact, but it rests on one assumption.
Square pixels and a flat panel
The calculation assumes square pixels and a flat, rectangular display — true for virtually all modern screens. Unusual panels with non-square subpixel layouts, curved geometry, or rounded corners can differ slightly from the computed value, and marketed "diagonal" sizes are sometimes rounded, so treat the result as a close estimate rather than a certified spec.