Screen PPI Calculator
Find pixel density from resolution and size.
Results update as you type.
How it works
A screen PPI calculator measures pixel density, the number of pixels packed into each inch of a display, from just three numbers: the horizontal resolution, the vertical resolution, and the diagonal size in inches. Higher PPI means finer detail and smoother text, which is why the same 1080p resolution looks razor-sharp on a phone but noticeably coarser stretched across a large monitor. Pixel density matters when comparing displays, choosing a monitor for design or coding work, or deciding how close you can sit before individual pixels become visible. Manufacturers quote resolution and screen size separately, but neither alone tells you how crisp the picture will be. PPI combines them into a single, comparable figure, so a 27-inch 4K panel and a 24-inch 1080p panel can be judged fairly side by side. The formula works by first finding the diagonal in pixels using the Pythagorean theorem on the width and height, then dividing by the diagonal in inches. Because the diagonal is measured in both pixels and inches, the division yields pixels per inch directly. Displays around 300 PPI or higher appear seamless at normal viewing distance. Shoppers, designers, and hardware reviewers use a PPI calculator to cut through marketing specs and compare screen sharpness honestly.
PPI = √(width² + height²) ÷ diagonal
The diagonal resolution in pixels comes from the Pythagorean theorem, since the horizontal and vertical pixel counts form the two sides of a right triangle whose hypotenuse spans the screen corner to corner. Dividing that diagonal pixel count by the physical diagonal length in inches gives pixels per inch. The method works because the diagonal is the one line whose length is quoted both in pixels and in inches.
Source:Standard digital media
We review all our tools from time to time to ensure accuracy.
Worked example
How to use this calculator
- 1
Enter your values
Enter horizontal resolution, vertical resolution and diagonal size.
- 2
Adjust the options
Fine-tune any options to match your situation.
- 3
Read your result
Pixel density updates instantly as you type — no button to press.
Frequently asked questions
What is a good PPI for a display?
It depends on viewing distance. Phones held close often exceed 400 PPI, while laptops look sharp around 200 to 300 PPI, and desktop monitors viewed further away read as crisp near 110 to 160 PPI. Beyond a certain density the eye cannot resolve individual pixels at normal distance, so higher numbers stop mattering. Judge PPI against how close you sit rather than chasing the largest figure.
Why use the diagonal instead of width or height?
Screen sizes are always quoted by their diagonal measurement, so that is the one physical length you know in inches. To divide pixels by inches you need a matching pixel length along the same line, which the Pythagorean theorem provides from the width and height. Using the diagonal keeps the pixel measurement and the inch measurement aligned along the same axis for a correct density.
Does higher PPI always look better?
Not necessarily. Once pixel density passes what your eye can distinguish at your viewing distance, extra PPI brings no visible improvement but can cost more and demand more graphics power. It can also make interface elements tiny unless the operating system scales them up. The right PPI balances sharpness, cost, and comfortable element sizes for how and where you actually use the screen.
What is the difference between PPI and DPI?
PPI, pixels per inch, describes the density of a digital display. DPI, dots per inch, describes how many ink dots a printer lays down per inch on paper. The terms are often used interchangeably, but they refer to different media. For on-screen sharpness you want PPI; for print quality you want DPI. This calculator deals strictly with screen pixel density in PPI.
Can I use this for any aspect ratio?
Yes. The formula uses the actual horizontal and vertical pixel counts, so it works for any aspect ratio, whether 16:9, 16:10, 4:3, or an ultrawide 21:9 panel. Just enter the true resolution and the diagonal size, and the Pythagorean calculation adapts automatically. That makes it equally valid for phones, tablets, laptops, standard monitors, and unusually wide or tall displays alike.