How PPI is Calculated?[What is PPI in Smartphone?]

Whenever we compare the screen of two smartphones then we always talk about PPI. Now, what is PPI, how much its quantity should be and how PPI is calculated? By reading this article you would be able to answer all these questions.

PPI full form is Pixel Per Inch. It is a metric that defines the pixel density or the sharpness of a screen. Now, to understand that, we have to first understand what a pixel is.

What is a Pixel? 

Any screen whether it is of a mobile, laptop, TV desktop is made up of many small components called pixels. On a screen, thousands or millions of pixels are arranged in a line.

A pixel is the smallest component that can show any color on the screen mobile screen. A pixel is further made up of three sub pixels, red, green, and blue lights, very tiny lights and with the help of these three colors others color pixels are made. If you want to see only blue color then you have to reduce green and red to zero and increase the blue color to full. Then the screen will become totally blue.

Similarly, if you want to see red then reduce blue and green to zero and increase red to full, then the screen will become fully red and if you want to see black then reduce red, green and blue to zero then the screen becomes black and if you want to see white then increase these three colors to full, then screen become fully white. That means by color mixing techniques you can see all other colors.

The screens which have high numbers of pixels will also have high screen details if the screen has a very low number of pixels then it will have low screen details as given in the picture below:-


Low Pixels

Low Pixel image

High Pixels

      high pixels image

How much PPI is good for Mobile?

A smartphone or a TV having a large number of pixels will show us better quality images or videos. The number of pixels depends upon the size of mobile phones. For example, if you have a 4-inch mobile phone and we put a 4k display in it then it is not going to benefit, rather it will cost more battery consumption because the 4 inch display is not so big that you can put so many pixels inside it.

When a human eye looks at a smartphone from a normal distance, then after a limit, it cannot differentiate in quality. If I give you a quad HD phone and a 4k phone, and I show you separately, you will not be able to judge the difference, so pixel density depends on the screen size and depends on how far you are watching it. Now you know what is pixel. Now its time to know what is PPI or Pixel Per Inch and how do we measure PPI?

How PPI is calculated?

what is PPI

In order to understand how PPI is calculated see the above image. This  image shows the screen of your phone, which is a full HD screen and we named ABCD for the four vertexes of the screen. Now full HD means 1080 x 1920, which means if we count from top to bottom then we get 1920 pixels and if we count from left to right, we get 1080 pixels. Hence, AB = 1920 and BC = 1080, so the total pixels are 1080 x 1920 = approx 2 million pixels (2 megapixels). It means your screen is 2 megapixels. Now, we talk about pixel density, let’s assume that the phone screen size is 5.5 inches. Now apply the Pythagoras theorem to know how many pixels size does AC has:-

AC      =          square root of [ (AB)² + (BC)² ]

=          square root of [ (1920)² + (1080)² ]

=          2202.90717

Now divide it by your phone screen size ie 5.5 inch

=          2202.90717 / 5.5

=          400.52 or 401 approx

It means 5.5 inch mobile screen has 401 pixels. Now we know how to calculate PPI and what is PPI.

To Calculate PPI you can also use the calculator


If your phone is between 350 to 450 pixels per inch, or if it is above 320, then it is absolutely fine.

Friends, I hope you will like this article and now you know what is PPI and how PPI is calulated, you will use it while buying a mobile phone, and you will not come only in the words of those people who say that quad HD is very good, less than it is useless, or 4k screen is the best because now you know that resolution or pixel per inch after a limit remains as a specification.

It is just the latest, so it is not necessarily good for you, even a 4.5 inch HD screen seems very good.

To know about types of display click here

Leave a comment