Ask iGyaan : What is ppi (pixels per inch) ?

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We often get similar questions from multiple users, this new section is to address exactly that, and we begin with the most asked question in recent times.

User Question :

Bharat Addresses to “ppi” in his videos, what does this mean? and does it have any relation to the camera resolution?

iG Answer :

PPI (pixels per inch), often referred to as pixel density is a measurement of the resolution of display of the device in question. this can also be the density of the images captured by a camera, but in Bharat’s reference it is always in terms of the display of the device in question.

PPI, is an actual count of the number of pixels found in one inch of a display, which varies depending on the resolution of the display and the overall size of the display.

Lets clarify further:

1. Calculate $d_p$ .

$d_p = \sqrt{w_p^2 + h_p^2}$

2. Calculate PPI:

$PPI = \frac{d_p}{d_i}$

where

$d_p$ is diagonal resolution in pixels,
$w_p$ is width resolution in pixels,
$h_p$ is height resolution in pixels and
$d_i$ is diagonal size in inches.

The HTC One M9+ has a screen resolution of 1440×2560 px

So, $d_p$ = [underoot of = (2073600 + 6553600)] =2937.2 (approx)

The diagonal size in inches is 5.2 inch, therefore $d_p$ / $d_i$ = 2937.2/5.2 = 564.84

Therefore the pixels per inch (ppi) of the HTC One M9+ = 565 (rounded)

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Comments

12 responses to “Ask iGyaan : What is ppi (pixels per inch) ?”

August 29, 2015

Samir Singh

4 saal pehle se pata hai mujhe ppi

Reply
August 29, 2015

Raghavendra Nasare

PPI OK. What are other factor influencing display quality?

Reply
August 29, 2015

Tanuj Kapoor

oh thats amazing U0001f60d thanks iGyaan, but my maths is very weak U0001f62d

Reply
August 28, 2015

Sandeep Mishra

Pythagoras theorem…simple

Reply
August 28, 2015

Shyam Kumar

Very good research by deviana

Reply
August 28, 2015

Prateek Gupta

Thanks

Reply
August 28, 2015

Harsh Kothari

Prateek Randhawa pls read bro! :)

Reply
June 30, 2013

Ankur Bisht

ppi is.no.of pixels in.an.inch :P

Reply
June 30, 2013

AbhilashKumar

what is the maximum resolution a human eye can identify..??

Reply
June 30, 2013

Droider

@Aarush Its clearly given in the post, anyways,
if I have a ‘5’ inch phone with 1280*720 resolution, then, square and add both the no’s in resolution!
[(1280)^2+(720)^2) = 2156800. Now take the square root of the number!
square root of 2156800 = 1468.6048.
Divide it by the screen size of the phone i.e. 5 inches!
1468.6048/5 = 293.721 which is approx. 294 PPI.
Ex: Canvas HD has 294 PPI. :)

Reply
June 30, 2013

Ashish Kumar

Here’s a python script for python guys:
import math as m
x = int(raw_input(“Enter X pixels t”))
y = int(raw_input(“Enter Y pixels t”))
ss = float(raw_input(“Enter screen size in inches t”))
ppi = m.sqrt(x*x + y*y)/ss
print “Screen density = “,ppi,” ppi”

Reply
June 30, 2013

Gogoi Chao Chatradhar

(Y)

Reply

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