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How to calculate the size of an image in KB?

morina88 Posted messages 21 Status Member -  
Armojax Posted messages 1863 Registration date   Status Member Last intervention   -
Hello everyone,

I've been searching for hours on how to calculate the size of an image in KB.

My data is as follows:

-Resolution: 75 PPI
-Size in cm: 4*3
-Grayscale: 4 bits (or 2^2)
-Number of bits/pixel: 2
-Size in KB?

If someone could kindly help me out? I know it's easy, but I'm afraid to make a mistake.

Thank you in advance!
Configuration: Windows 7 / Firefox 3.5.8

5 answers

  1.
    Armojax Posted messages 1863 Registration date   Status Member Last intervention   1 529
     
    Good evening Morina,

    - 4 cm is: 4 / 2.54 = 1.575 inches (1 inch = 2.54 cm).
    At 75 DPI, that gives: 1.575 x 75 = approx. 118 pixels for the image width

    - with the same calculation, we find approx. 89 pixels for the image height.

    - number of pixels: 118 x 89 = approx. 10500 pixels

    - with 2 bits per pixel (according to your data), you fit 4 pixels into one byte. So the image takes up 10500 / 4 = 2625 bytes.

    - 1 kilo = 1000. So the image weighs 2.625 kB (kilobytes)
    - now, if we're talking about binary kilo which is 1024 bytes, it's better to say kibi-byte, and the image weighs about 2.56 kibi.


    Taking into account your data (4 levels of gray).
    16