PPI Calculator
Find a display's pixel density (pixels per inch).
Results update as you type.
How it works
Pixel density, measured in pixels per inch or PPI, describes how sharp a display looks, and this calculator finds it from the resolution and screen size. You enter the horizontal and vertical pixel counts and the diagonal size in inches, and it returns the PPI along with the dot pitch, the physical spacing between pixels, in millimeters. The method uses the Pythagorean theorem to find the diagonal resolution in pixels from the width and height, then divides by the diagonal screen size to get pixels per inch. PPI matters because it, not resolution alone, determines perceived sharpness: the same 1920-by-1080 resolution looks crisp on a small phone but coarse stretched across a large monitor, because the pixels are spread over more inches. Higher PPI means smaller, denser pixels, smoother text, and less visible pixelation. Phones now exceed 400 PPI, laptops and high-end monitors often sit between 150 and 250, and large TVs viewed from a distance get by with much less. Dot pitch is the inverse view, the millimeters between pixels, historically used to rate monitors. Use this to compare displays, judge whether a screen is sharp enough for your viewing distance, and understand marketing resolution claims. Enter the resolution and diagonal size to compute PPI.
PPI = √(width² + height²) / diagonal
Pixel density is the diagonal resolution in pixels, found with the Pythagorean theorem from the horizontal and vertical pixel counts, divided by the screen's diagonal size in inches. Dot pitch, the distance between pixels, is 25.4 millimeters divided by the PPI. Higher PPI means finer detail and smoother-looking text and images.
Source:Display technology
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 PPI?
PPI, or pixels per inch, is a measure of a display's pixel density, meaning how many pixels are packed into each inch of screen. Higher PPI means finer detail and smoother-looking text and images. It is calculated from the resolution and the diagonal screen size, and it determines perceived sharpness better than resolution alone.
How do I calculate PPI?
Find the diagonal resolution in pixels using the Pythagorean theorem on the horizontal and vertical pixel counts, then divide by the diagonal screen size in inches. For 1920 by 1080 on a 15.6-inch screen, that is about 141 PPI. The calculator does this instantly and also gives the dot pitch.
Why does the same resolution look different on different screens?
Resolution is the total pixel count, but PPI accounts for how those pixels are spread across the physical screen size. A 1080p resolution looks sharp on a small phone because the pixels are dense, but coarse on a large monitor where the same pixels cover more inches, lowering PPI and making individual pixels more visible.
What is a good PPI?
It depends on viewing distance. Phones held close benefit from 300 PPI or more, laptops and monitors viewed at arm's length look sharp around 150 to 220 PPI, and large TVs seen from across a room need far less. Beyond a certain density for a given distance, the eye cannot resolve more detail.
What is dot pitch?
Dot pitch is the physical distance between adjacent pixels, usually in millimeters, and is the inverse of PPI. A smaller dot pitch means pixels are closer together and the image is sharper. It was a common spec for older monitors. The calculator reports dot pitch alongside PPI, converting between the two automatically.