Talk:Data compression ratio

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"The 10MB file that compresses to 2 MB would have ((10-2)/10)*100% = 80% compression ratio."

Is this formula really true? The table provided in doesn't complain to it at all. --riba 01:40, 7 February 2006 (UTC)

And what about compression ratios greater than 100

( (1000 - 1) / 1000 ) * 100 = 99,9% ?

so this sux

I agree. I've never seen a compression ratio expressed like this. Changing article.

Unfortunately, the formula used on the site, as well as the table at, ignore the terminology used throughout many decades of data compression research and technology. Ratio means ratio, and a higher compression ratio means higher compression. I'll add some references. AndreasWittenstein 07:12, 27 March 2007 (UTC)BitJazz

NOTE: People confuse compression factor with compression ratio. See: [Data compression: the complete reference By David Salomon]. The correct formula is CR=output/input, and hence a lower value of CR is better. Please cite at least a peer-reviewed article before changing this formula again.


There seems to be no general concensus about the terminology even in the literature. In [Khalid Sayood: Introduction to Data Compression (Morgan Kaufmann, 2nd Ed., 2006)] the compression ratio is defined on page 5 like this:

Ratio of the number of bits required to represent the data before compression to the number of bits required to represent the data after compression.

So this leads to CR=input/output, the inverse of the definition by Salomon.

I believe that Sayood's definition is used more often than Salomon's, see the comments above. To me, a compression ratio of 4:1 (4 bytes are compressed to 1 byte) looks more natural than 1:4. I'm adding a dispute marker to the article. Voxelizer (talk) 11:23, 17 June 2010 (UTC)


needs clean up needs refs and soucres needs a link section as wellOo7565 20:16, 29 May 2007 (UTC)

There will be two things. Do not confuse with compression factor and compression ratio. The meaning of compression is to minimize the image.

Compression ratio=(total number of bits at input)/(total number of bits at output)i.e. 10:1,100:1,20:2 in this way.

Compression factor = (output bits/input bits) Compression Factor should be equal to or less than 1 and ratio should be grater than 0.

— Preceding unsigned comment added by (talk) 10:10, 27 September 2011 (UTC)


Why express the compression ratio of 1080i video, when you have to account for interlacing which muddies the waters? I say 1080p or 720p should be used to replace that little factoid, so it's easier to compute mentally and for users to understand. Bumblebritches57 (talk) 02:10, 31 August 2013 (UTC)

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