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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) = dp / di
dp = âˆš w2p + h2p

Where,
dp= Diagonal resolution
wp = Width of the screen
hp = Height of the screen
di = 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.
di = 21.5 inch
wp = 1024
hp = 768

Step 2: Find dp (Diagonal resolution) of the LCD.
dp = âˆš w2p + h2p
= âˆš(1024)2 + (768)2
= âˆš 1048576 + 589824

Step 3: Diagonal Resolution = âˆš 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 = dp / di
=1280/21.5

Step 6: Pixels Per Inch / Pixel Density = 59.5