Screen Size Calculator — Diagonal to Width, Height & PPI
Screen Width
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Screen Height
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Screen Area
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PPI (Pixels Per Inch)
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Dot Pitch
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Total Pixels
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How This Calculator Works
This screen size calculator helps you determine the exact physical width and height of any display based on its diagonal measurement and aspect ratio. It also calculates PPI (pixels per inch) when you provide the screen resolution, giving you a complete picture of your display's specifications.
The calculation uses the Pythagorean theorem combined with the aspect ratio. For a 16:9 display, the width-to-height ratio is 16:9, so the diagonal forms the hypotenuse of a right triangle with those proportions. The formula derives width = diagonal × 16/√(16²+9²) and height = diagonal × 9/√(16²+9²). PPI is calculated as √(horizontalPixels² + verticalPixels²) / diagonal.
Understanding screen dimensions and pixel density is essential when choosing monitors, TVs, projector screens, or phone displays. Higher PPI means crisper images and text, which is especially important for tasks like photo editing, reading, and design work. Use this calculator to compare displays before making a purchase decision.
Frequently Asked Questions
How do I calculate screen width and height from diagonal size?
Using the aspect ratio (e.g., 16:9), the diagonal, and the Pythagorean theorem: Width = Diagonal × (AspectWidth / √(AspectWidth² + AspectHeight²)), and Height = Diagonal × (AspectHeight / √(AspectWidth² + AspectHeight²)).
What is PPI and why does it matter?
PPI (Pixels Per Inch) measures pixel density — how many pixels fit in one inch of screen. Higher PPI means sharper text and images. A 27-inch 4K monitor has ~163 PPI, while a 27-inch 1080p monitor has only ~82 PPI. For comfortable desktop use, 90-110 PPI is standard; for retina-quality displays, 200+ PPI is ideal.
What are common aspect ratios for monitors and TVs?
The most common aspect ratio is 16:9, used by most TVs and monitors. Ultrawide monitors use 21:9 or 32:9. Older displays used 4:3 or 5:4. Phones often use 19.5:9 or 20:9. Tablets typically use 4:3 or 3:2.
How does screen size affect viewing distance?
A general rule is to sit 1.5 to 2.5 times the diagonal screen size away for TVs. For monitors, 20-26 inches for 24" screens and 25-34 inches for 27-32" screens. Larger screens or higher resolutions allow closer viewing without seeing individual pixels.
What PPI do I need for sharp text on a monitor?
For desktop monitors at typical viewing distances of 20 to 30 inches, 90 to 110 PPI provides comfortable readability for most users. For sharp, retina-quality text, aim for 130 PPI or higher. A 27-inch 4K monitor delivers about 163 PPI, which most users find exceptionally crisp. Graphic designers and photographers often prefer 4K or 5K monitors at 27 to 32 inches for pixel-level detail in their work.
Is a 32-inch 4K monitor better than a 27-inch 4K monitor?
It depends on your priorities. A 27-inch 4K monitor has higher pixel density (approximately 163 PPI) resulting in sharper text and images. A 32-inch 4K monitor has lower density (approximately 138 PPI) but provides more physical screen area for multitasking. At normal desk viewing distances of 24 to 30 inches, most users find 27-inch 4K monitors ideal for sharpness, while 32-inch 4K works better if you sit further back or need more usable space for side-by-side windows.