Screen PPI Calculator
Find a display's pixels per inch.
Pixel density tells you how sharp a screen looks.
How the Math Works
The Screen PPI Calculator uses the Pythagorean theorem to determine pixel density. By taking the square root of the sum of the squared width and height resolutions (√(width² + height²)), it calculates the diagonal pixel count. Dividing this value by the screen's diagonal size in inches yields the pixels per inch (PPI), which quantifies how densely packed the pixels are on a display.
Practical Applications
To use this calculator, first measure the screen's width and height in pixels from its resolution (e.g., 1920x1080). Locate the diagonal screen size in inches (e.g., 13.3 inches for a laptop). Input these values into the formula: PPI = √(width² + height²) ÷ diagonal. For example, a 1920x1080 screen with a 13.3-inch diagonal would calculate as √(1920² + 1080²) ÷ 13.3 ≈ 166 PPI. This provides a standardized metric for comparing display quality across devices.
Day-to-Day Use
Understanding PPI helps consumers make informed choices when purchasing devices like smartphones, tablets, or monitors. Higher PPI values indicate sharper images and smoother text, which enhances readability and visual experience. This is especially important for tasks like photo editing, video streaming, or prolonged screen use, where display clarity directly impacts comfort and productivity. By comparing PPI values, users can prioritize devices with superior screen quality for their specific needs.
Worked example
1920×1080 on 24 in → 91.8 PPI.
FAQ
What's 'retina'?
Roughly 300+ PPI at typical viewing distance, where pixels become indistinguishable.