Enter the horizontal and vertical resolution in pixels and the diagonal screen size in inches. Pixel density is the diagonal length in pixels, from the Pythagorean theorem, divided by the diagonal in inches. Use the marketed diagonal, which is the visible measurement.
The pixel pitch is 25.4 millimeters divided by the PPI, the distance between neighboring pixel centers.
PPI (Pixels Per Inch): worked example
| Horizontal resolution (pixels) | 2,560 |
|---|---|
| Vertical resolution (pixels) | 1,440 |
| Screen diagonal (inches) | 27 |
| Pixels per inch | 108.8 |
| Pixel pitch (mm) | 0.233 |
PPI (Pixels Per Inch): formula
Sharpness also depends on viewing distance, subpixel layout and the panel type. Printed PPI, or DPI, refers to the print resolution and is a separate concept. High PPI needs more graphics power and can make text small without scaling.
Marketing diagonals are sometimes rounded.
Common error: Comparing resolutions across different screen sizes. A phone with fewer pixels can look far sharper than a larger display with more, because the pixels are packed tighter.
PPI (Pixels Per Inch): changing Horizontal resolution (pixels)
| Horizontal resolution (pixels) | Pixels per inch | Pixel pitch (mm) |
|---|---|---|
| 2,048 | 92.7 | 0.274 |
| 2,304 | 100.6 | 0.252 |
| 2,560 (example) | 108.8 | 0.233 |
| 2,816 | 117.1 | 0.217 |
| 3,072 | 125.7 | 0.202 |
PPI (Pixels Per Inch): compare input ranges
| Input | Tested from | To | Pixels per inch: low input | Pixels per inch: high input | Swing |
|---|---|---|---|---|---|
| Screen diagonal (inches) | 24 | 30 | 122.4 | 97.9 | 24.5 (23%) |
| Horizontal resolution (pixels) | 2,304 | 2,816 | 100.6 | 117.1 | 16.5 (15%) |
| Vertical resolution (pixels) | 1,296 | 1,584 | 106.3 | 111.5 | 5.2 (4.8%) |
PPI (Pixels Per Inch): individual input comparisons
| Input | Value | Pixels per inch | Pixel pitch (mm) |
|---|---|---|---|
| Horizontal resolution (pixels) | 2,048 | 92.7 | 0.274 |
| 2,304 | 100.6 | 0.252 | |
| 2,560 | 108.8 | 0.233 | |
| 2,816 | 117.1 | 0.217 | |
| 3,072 | 125.7 | 0.202 | |
| Vertical resolution (pixels) | 1,152 | 104 | 0.244 |
| 1,296 | 106.3 | 0.239 | |
| 1,440 | 108.8 | 0.233 | |
| 1,584 | 111.5 | 0.228 | |
| 1,728 | 114.4 | 0.222 | |
| Screen diagonal (inches) | 22 | 133.5 | 0.19 |
| 24 | 122.4 | 0.208 | |
| 27 | 108.8 | 0.233 | |
| 30 | 97.9 | 0.259 | |
| 32 | 91.8 | 0.277 |
PPI (Pixels Per Inch): combined input changes
| Horizontal resolution (pixels) / Vertical resolution (pixels) | 1,152 | 1,440 | 1,728 |
|---|---|---|---|
| 2,048 | 87 | 92.7 | 99.2 |
| 2,304 | 95.4 | 100.6 | 106.7 |
| 2,560 | 104 | 108.8 | 114.4 |
| 2,816 | 112.7 | 117.1 | 122.4 |
| 3,072 | 121.5 | 125.7 | 130.5 |
PPI (Pixels Per Inch): which assumptions move the result?
PPI (Pixels Per Inch): values and definitions
| Quantity and definition | Value used |
|---|---|
| Horizontal resolution (pixels) | 2,560 |
| Vertical resolution (pixels) | 1,440 |
| Screen diagonal (inches) | 27 |
| Pixels per inch | 108.8 |
| Pixel pitch (mm) | 0.233 |
PPI (Pixels Per Inch): half and double Screen diagonal (inches)
| Screen diagonal (inches) | Pixels per inch |
|---|---|
| 13.5 | 217.6 |
| 27 | 108.8 |
| 54 | 54.4 |
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Sharpness on a screen depends on how many pixels fit into each inch, not on the resolution number alone. A 27-inch monitor with 2560 by 1440 pixels packs about 109 per inch, while the same resolution on a 32-inch panel spreads to about 92. The pixel pitch output gives the same idea as a distance, roughly 0.23 millimeters between pixel centers here.
Measure the diagonal of the visible screen. Advertised sizes are rounded, and a half-inch difference shifts the density by a few percent.
Find the shape of the screen on the aspect ratio calculator, the size of a file on the storage converter and the data a stream uses on the bandwidth calculator. The Pythagorean theorem and distance calculators show the diagonal math.
Does PPI alone tell me a display is comfortable?
No. Viewing distance, text scaling, vision and the panel affect that choice. This equation computes geometric pixel density.
Does doubling resolution at the same diagonal double PPI?
Doubling both pixel dimensions doubles diagonal pixel count and PPI, while total pixel count becomes four times as large.
What is a good PPI for a monitor?
Compare pixel density with the actual viewing distance, text scaling and eyesight. Values such as 110, 140 or 165 PPI describe different pixel spacing, not universal quality thresholds. Two equally sized screens can require different interface scaling, so the calculated density alone cannot predict comfort or readable text size.
How is PPI calculated?
Take the square root of width squared plus height squared, in pixels, and divide by the diagonal size in inches.
Is PPI the same as DPI?
No. PPI describes a screen's pixel density, and DPI describes the dots a printer lays down per inch.