How to Calculate PPI

How to find Pixel Density (PPI) of a screen?

Pixels Per Inch (Pixel Density) Calculation

PPI (Pixels Per Inch) is the measurement of the pixel density (sharpness) of any display screen. It is used in the measurement of screen resolution of electronic devices like computer, mobile phones, television etc., Here is a simple step by step tutorial to measure the pixel density of the screen.

Formula :
Pixels per inch (PPI) = d_p / d_i
d_p = √ w²_p + h²_p

Where,
d_p= Diagonal resolution
w_p = Width of the screen
h_p = Height of the screen
d_i = Diagonal Size (in inches)

Example: Consider a 21.5 inch LCD TV with the screen resolution of 1024 x 768. Find the PPI of the LCD.
d_i = 21.5 inch
w_p = 1024
h_p = 768

Step 2: Find d_p (Diagonal resolution) of the LCD.
d_p = √ w²_p + h²_p
= √(1024)² + (768)²
= √ 1048576 + 589824

Step 3: Diagonal Resolution = √ 1638400

Step 4: We got the Diagonal Resolution as 1280

Step 5: To find the pixels per inch of a LCD, substitute the obtained values in the formula.
PPI = d_p / d_i
=1280/21.5

Step 6: Pixels Per Inch / Pixel Density = 59.5

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