What is the ordering of size following image types : RGB,grayscale, indexed image, binary image?

RGB highest size?and binary lowest?

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    $\begingroup$ You can store a binary image less efficiently than a RGB image – there's no direct relation. Indexed doesn't say how large your palette is; neither does "grayscale" nor "RGB" say how many bits are used per chanel, so really, no general statement can be given. You're showing very strong signs of the XY Problem here! Please remedy that. Generally, if your question is only two sentences, you probably could have done better explaining how this question arose and what you've researched so far – not the first time I tell you. $\endgroup$ Apr 24, 2020 at 20:54
  • $\begingroup$ To explain my downvote explicitly: votes are used to assess the quality of a question, especially in terms of showing how hard it would have been for the asker of a question to at least find a partial answer on their own. $\endgroup$ Apr 24, 2020 at 20:55

1 Answer 1


Binary images are clearly smallest in terms of size, followed by indexed (paletted) images. RGB and greyscale images can take different sizes.

There are also (A)RGB images with sizes up to 48 bits but they usually include an extra alpha channel (for transparency purposes) so I haven't described them below.

RGB (red, green, blue ) - 24 bits (each colour channel takes up 8 bits of space )

RGB (red, green, blue ) - 16 bits ( the green channel usually takes up 6 bits )

RGB (red, green, blue ) - 15 bits ( 5 bits per channel)

RGB (red, green, blue ) - 8 bits ( usually encoded as rrrgggbb )

Greyscale image - 8 - 24 bits ( each colour channel in a greyscale image has the same value)

Indexed image - usually 8 bits ( the pixels don't carry colour information at all--rather they are indices into a colour table (i.e a palette). An 8-bit palette can hold 256 colours. While larger palettes are possible, they're rarely used because the most important reason to use a palette is to conserve space )

Binary image - 1 bit ( in a binary image, each pixel is stored as 1 bit. Since 1 bit can encode only 2 values (0 or 1), this kind of image can display only 2 colours (e.g black and white etc. )


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