PPI Calculator
Calculate pixel density (pixels per inch) from screen resolution and diagonal size.
This tool is for informational and educational purposes only. It is not a substitute for professional financial, medical, legal, or engineering advice. See Terms of Service.
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Request a ToolHow to Use the PPI Calculator
- Select a resolution preset or enter the horizontal and vertical pixel counts manually. You can find the resolution in your display settings or the device specifications page.
- Enter the diagonal screen size in inches. This is the measurement from corner to corner of the active screen area.
- Read the results. The calculator shows the PPI value, total pixel count, megapixel count, and a density classification from low to retina quality.
PPI is calculated as: PPI = sqrt(width² + height²) / diagonal. This measures the density of pixels packed into each inch of the screen.
About Pixels Per Inch
Pixels per inch (PPI) describes how densely pixels are packed on a screen. Higher PPI means sharper text and images. Apple coined the term "Retina display" to describe screens where individual pixels are too small to distinguish at normal viewing distance — typically around 300 PPI for phones held at arm's length, or around 200 PPI for monitors viewed at desk distance.
A 1080p (1920x1080) display at 24 inches has about 92 PPI, which is standard for desktop monitors. The same resolution on a 5.5-inch smartphone would be about 401 PPI, which Apple would classify as Retina. This is why pixel counts must always be evaluated relative to screen size and viewing distance.
Note that PPI (pixels per inch) and DPI (dots per inch) are often used interchangeably for displays but technically differ: PPI measures physical screen pixels, while DPI historically refers to printer ink dots per inch.
Frequently Asked Questions
What PPI is considered retina quality?
Apple's Retina threshold varies by viewing distance. For iPhones held close, about 300 PPI qualifies. For iPads and laptops viewed slightly farther away, about 200-220 PPI. For desktop monitors at desk distance, 150+ PPI is usually crisp enough that pixels are invisible. The key question is whether pixels are distinguishable at your normal viewing distance.
What is the PPI of the iPhone 15?
The iPhone 15 has a 2556x1179 pixel resolution on a 6.1-inch screen, which calculates to approximately 461 PPI. The iPhone 15 Pro has a 2556x1179 pixel display on a 6.1-inch screen at the same PPI. Both are well above the threshold where individual pixels are visible at normal phone-viewing distances.
Is 4K better than 1080p on a 27-inch monitor?
A 4K (3840x2160) 27-inch monitor has about 163 PPI, while 1080p at 27 inches is about 82 PPI. The 4K display is noticeably sharper for text, fine details, and high-resolution photos. At normal desk viewing distances (24-30 inches), most people can see the difference clearly. For gaming at that size, the difference depends more on frame rate capabilities and rendering performance.
What resolution do I need to print at 300 DPI?
Multiply the print size in inches by 300 to get the required pixel count. An 8x10 print at 300 DPI requires a 2400x3000 pixel image (7.2 megapixels). A 16x20 print at 300 DPI requires 4800x6000 pixels (28.8 megapixels). For standard viewing distances, 150-200 DPI is often sufficient for large prints.