Practical
Device Pixel Ratio Calculator
Calculate device pixel ratio, PPI, and ideal image resolution for any screen
Device Pixel Ratio (DPR) is the ratio between physical pixels and logical CSS pixels. On Retina displays, one CSS pixel maps to 4 or 9 physical pixels, requiring higher-resolution images.
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Tip: Use SVG for icons and simple graphics - they render perfectly at any DPR without requiring additional image assets.
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Fun Fact
Steve Jobs defined Retina as displaying above 300 PPI at typical viewing distance. The original iPhone 4 hit exactly 326 PPI at launch.
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