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如何计算Screen PPI

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Pixels Per Inch (PPI) — also called pixel density — measures how many pixels fit into one linear inch of a display. Higher PPI means sharper images. Apple introduced the term 'Retina Display' for screens with PPI high enough that individual pixels are not distinguishable at a typical viewing distance (generally ≥ 200–300 PPI depending on screen size and viewing distance).

公式

Diagonal pixel count = √(width² + height²) in pixels

分步指南

  1. 1Diagonal pixel count = √(width² + height²) in pixels
  2. 2PPI = diagonal pixel count / diagonal screen size in inches
  3. 3Dot pitch = 25.4 mm / PPI — physical size of one pixel
  4. 4Total megapixels = (width × height) / 1,000,000

例题解析

输入
1920×1080 @ 24 inches
结果
91.8 PPI — standard 1080p monitor
Not retina — pixels visible if close up
输入
3840×2160 @ 27 inches (4K)
结果
163.2 PPI
Better, still not retina at arm's length
输入
2556×1179 @ 6.1 inches (iPhone 15)
结果
460 PPI — Retina Super Retina XDR

常见问题

What is Screen Ppi?

Pixels Per Inch (PPI) — also called pixel density — measures how many pixels fit into one linear inch of a display. Higher PPI means sharper images

How accurate is the Screen Ppi calculator?

The calculator uses the standard published formula for screen ppi. Results are accurate to the precision of the inputs you provide. For financial, medical, or legal decisions, always verify with a qualified professional.

What units does the Screen Ppi calculator use?

This calculator works with inches. You can enter values in the units shown — the calculator handles all conversions internally.

What formula does the Screen Ppi calculator use?

The core formula is: Diagonal pixel count = √(width² + height²) in pixels. Each step in the calculation is shown so you can verify the result manually.

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