Pixel density is an important factor affecting the quality of images displayed on screens. High pixel density leads to sharper images and better overall visual quality, making it vital to understand how to calculate pixels per inch (PPI). In this article, we will cover the basics of PPI, discuss its importance, and provide a step-by-step guide on calculating it.

What is PPI?

Pixels per inch (PPI) is a measurement that quantifies the number of pixels in a specific area of a digital display, usually an inch. It represents the number of pixels horizontally and vertically within one square inch of screen space. Typically, higher PPI values lead to sharper images with finer details.

Importance of PPI

PPI is an important factor in determining image sharpness and clarity on any digital display. Higher PPI values provide smoother edges and finer details in images. This is particularly relevant for smartphones, tablets, computer monitors, and TV displays.

A low-PPI device may lack detail because adjacent pixels are further apart, resulting in a “blocky” or pixelated appearance. In contrast, high-PPI devices are less likely to exhibit this issue because pixels are packed more densely.

Calculating PPI

To calculate the PPI value of a display, you will need three pieces of information:

1. Screen resolution: The number of horizontal and vertical pixels in the display

2. Screen size: The diagonal measurement of the screen (either in inches or centimeters)

3. Aspect ratio: The width-to-height ratio of the display

Here’s a step-by-step guide on how to calculate PPI:

Step 1: Determine the screen resolution

Obtain the horizontal (x) and vertical (y) pixel count for your display.

Step 2: Calculate the aspect ratio

The aspect ratio can be written as W:H; for example, 16:9 is a common aspect ratio for widescreen displays. Aspect ratios help to identify the display’s width and height proportions.

Step 3: Calculate the screen dimensions

Using the aspect ratio, derive the width (A) and height (B) of your screen. Using Pythagorean theorem formula, A^2 + B^2 = C^2 (where C is the diagonal screen size), you can solve for A and B.

Step 4: Calculate PPI

Finally, you can use this formula to calculate PPI:

PPI = √(x² + y²) ÷ C

For example,

Screen resolution: 1920 x 1080 pixels

Diagonal size: 21.5 inches

Aspect ratio: 16:9

Width (A) = 16x; Height (B) = 9x

Squared width (a²) + squared height (b²) = squared diagonal size (c²)

Substituting values:

(16x)^2 + (9x)^2 = (21.5)^2

256x^2 +81x^2 = 462.25

Solving for x:

337x^2 = 462.25

x ≈ √(462.25/337)

x ≈ √1.371

x ≈ 1.171

Width = 1.171 *16 = 18.736 inches

Height = 1.171 *9 =10.539 inches

Calculating PPI using the formula:

PPI = √(1920² + 1080²) ÷ 21.5 ≈︎102

Note that you can utilize online tools to calculate PPI, eliminating manual calculations.