# Compression ratio of Windows file compression

**URL:** <https://boards.straightdope.com/t/compression-ratio-of-windows-file-compression/550470>\
**Category:** Factual Questions\
**Created:** [August 16, 2010, 11:20pm UTC](https://boards.straightdope.com/t/compression-ratio-of-windows-file-compression/550470 "2010-08-16T23:20:22Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![Nobody](https://avatars.discourse-cdn.com/v4/letter/n/94ad74/32.png) [@Nobody](https://boards.straightdope.com/u/Nobody)\
**Post date:** [August 16, 2010, 11:20pm UTC](https://boards.straightdope.com/t/compression-ratio-of-windows-file-compression/550470/1 "2010-08-16T23:20:22Z")

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Just out of curiosity, what is the compression ratio for Windows file compression? I’m talking about when you right click a drive/folder/file, click properties, click advanced, and check the box that says “Compress contents to save disk space”.

I’ve tried Googling this, but my Google-fu is weak

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**Author:** ![Indistinguishable](https://avatars.discourse-cdn.com/v4/letter/i/90ced4/32.png) [@Indistinguishable](https://boards.straightdope.com/u/Indistinguishable)\
**Post date:** [August 16, 2010, 11:21pm UTC](https://boards.straightdope.com/t/compression-ratio-of-windows-file-compression/550470/2 "2010-08-16T23:21:44Z")

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It depends on what you’re compressing…

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**Author:** ![Nobody](https://avatars.discourse-cdn.com/v4/letter/n/94ad74/32.png) [@Nobody](https://boards.straightdope.com/u/Nobody)\
**Post date:** [August 16, 2010, 11:35pm UTC](https://boards.straightdope.com/t/compression-ratio-of-windows-file-compression/550470/3 "2010-08-16T23:35:31Z")

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I’m talking typical ratios. For example zip files typically have 2:1 (but can go higher).

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**Author:** ![Reply](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/reply/32/15952_2.png) [@Reply](https://boards.straightdope.com/u/Reply)\
**Post date:** [August 16, 2010, 11:52pm UTC](https://boards.straightdope.com/t/compression-ratio-of-windows-file-compression/550470/4 "2010-08-16T23:52:58Z")

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(I’m not an expert on this, but)  
According to [this page](http://msdn.microsoft.com/en-us/library/aa364219%28VS.85%29.aspx), NTFS compression uses a variant of the Lempel-Ziv algorithm, which forms a partial basis of many other compression schemes – zip files often use LZMA, a combination of that and something else) for example.

I’d expect roughly the same 2:1 ratios for plaintext and such, but I’m really just pulling that number out of my ass. I’d say compression ratios don’t matter much these days with disk space being so cheap and most media (pictures, movies, sound) being already ruthlessly compressed.

Using the “compact” command from a terminal window will show you the exact ratio of compressed files.

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<div class="post-metadata">

**Author:** ![Nobody](https://avatars.discourse-cdn.com/v4/letter/n/94ad74/32.png) [@Nobody](https://boards.straightdope.com/u/Nobody)\
**Post date:** [August 16, 2010, 11:54pm UTC](https://boards.straightdope.com/t/compression-ratio-of-windows-file-compression/550470/5 "2010-08-16T23:54:17Z")

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Thank you.

Edit: I didn’t even think to just Google NTFS compression ratio, but doing so gave me a link to [this](http://www.snapfiles.com/get/ntfsratio.html) program which tells you the ratios of compressed files.