PPI Pixel Density Calculator

Enter Calculation

Horizontal Resolution (Width) pixels

Vertical Resolution (Height) pixels

Diagonal Screen Size

Unit inches centimeters millimeters

Formula

Show calculation steps (1)

1. Dot Pitch

   

   Physical distance between pixel centers, in millimeters.

Results

Pixel Density (PPI)

141.21

pixels per inch

Aspect Ratio	16:9
Diagonal Resolution	2,202.91 pixels
Total Pixels	2,073,600 pixels (2.07 MP)
Pixels per Square Inch (PPI²)	19,941 px/in²
Screen Width	13.6 in
Screen Height	7.65 in
Dot Pitch	0.1799 mm

What is PPI (Pixel Density)?

PPI stands for pixels per inch, a measure of how densely pixels are packed on a display. Higher PPI means a sharper, more detailed image because individual pixels become harder to distinguish. This calculator derives PPI and several related screen metrics from a display's pixel resolution and its diagonal screen size. It works for phones, tablets, monitors, laptops and TVs, and it is a pure geometric calculation that applies universally.

Higher PPI packs more pixels into the same area, producing a sharper image.

How to Use It

Enter the horizontal resolution (width in pixels), the vertical resolution (height in pixels), and the diagonal screen size. Choose whether the diagonal is given in inches, centimeters or millimeters — the tool converts it to inches internally (2.54 cm or 25.4 mm per inch) because PPI is defined per inch. The result shows pixel density plus dot pitch, physical width and height, total pixels, pixels per square inch and the reduced aspect ratio.

The Formula Explained

First the diagonal resolution in pixels is found with the Pythagorean theorem: \(dp = \sqrt{W^2 + H^2}\). Dividing that by the diagonal size in inches gives PPI:

$$\text{PPI} = \dfrac{\sqrt{W^2 + H^2}}{D}$$

From PPI, dot pitch is \(25.4 / \text{PPI}\) mm, and the physical width and height are \(W / \text{PPI}\) and \(H / \text{PPI}\) inches. The aspect ratio reduces W:H by their greatest common divisor.

The diagonal pixel count is found from width and height using the Pythagorean theorem, then divided by physical diagonal D.

Worked Example

A 1920×1080 display on a 15.6-inch diagonal:

$$dp = \sqrt{1920^2 + 1080^2} = \sqrt{4{,}852{,}800} \approx 2202.91 \text{ pixels}$$$$\text{PPI} = \dfrac{2202.91}{15.6} \approx 141.2$$$$\text{Dot Pitch} = \dfrac{25.4}{141.2} \approx 0.18 \text{ mm}$$

Total pixels = 2,073,600 (about 2.07 MP). The aspect ratio reduces to 16:9.

FAQ

What is a good PPI? Phones often exceed 300–500 PPI; desktop monitors typically sit around 90–160 PPI. Higher is sharper, but the benefit depends on viewing distance.

Why does the diagonal need converting to inches? PPI literally means pixels per inch, so the diagonal must be expressed in inches before dividing.

What is dot pitch? It is the physical spacing between pixel centers in millimeters — the inverse view of pixel density. Smaller dot pitch means a finer display.