FLAC Compression Levels Explained and Compared

Norvan Martin

Let’s say you have a new music system and you want to rip all your music to FLAC to take advantage of your high-quality setup. One of the most important considerations is which FLAC compression level you should choose. On the other hand, maybe you are ripping your music to archive them. Which FLAC level should you choose? In this article, we explain FLAC compression levels and help you choose the best option for your needs. 

What Are FLAC Compression Levels?

FLAC is short for Free Lossless Audio Codec which means there is no loss of quality. It is a popular open-source lossless compression file format that offers CD-quality audio sound at half the size. FLAC offers varying levels of lossless compression from 1 through to 8 which are tailored to balance file size with encoding time. 

Here’s a detailed look at the various FLAC compression levels:

Level 0:

This is the speediest compression level, yielding larger file sizes. Ideal for scenarios where time is of the essence and file size is a secondary concern.

Level 1:

Marginally slower than Level 0, this level offers somewhat smaller file sizes as a trade-off for the slight decrease in speed.

Level 2:

This level finds a happy medium between encoding duration and file size, making it a popular default setting in many applications.

Level 3:

Opt for this when a smaller file size is preferred over the compression time offered by Level 2, albeit at a slightly slower pace.

Level 4:

A bit slower than Level 3, with the potential for only modest reductions in file size. It’s considered an intermediate option.

Level 5:

Often recommended as the optimal choice, Level 5 provides a balanced compromise between decent compression and reasonable encoding speed.

Level 6:

Offers tighter compression compared to Level 5, but at a noticeably slower encoding speed.

Level 7:

Less commonly used, as it’s slower than Level 6 and only provides a marginal improvement in file size reduction.

Level 8:

The pinnacle of FLAC compression, delivering the smallest file sizes at the cost of the longest encoding times. Best suited for situations where minimizing file size is paramount.

As you ascend through the levels, the compression improves but at the expense of longer encoding times.

The actual impact on file size and encoding duration varies based on the specific audio content and the processing capabilities of your computer. For the average user, Levels 5 or 6 often offer an effective balance, yielding moderately sized files without overly prolonged encoding times.

FLAC Compression Levels 0 to 8 chart

FLAC compression levels determine the file size of the compressed file. When FLAC files are compressed, there is no loss of quality because FLAC will always decode into the exact uncompressed audio track down to every single bit.

The only difference between the compression levels is the resulting file size. With other compression methods, such as MP3, various aspects of the files are stripped out to save space. Check out our article on MP3 vs FLAC

However, the disadvantage of using high FLAC compression to save space is that the compression will take longer. The more space you save, the longer the compression process will take. 

Example FLAC Compression

Much theoretical literature will tell you that there should be no noticeable difference in the decoding process when decoding FLAC files at different FLAC levels. However, is this true? 

We ran a test to check this out. Firstly, we ripped the song into an uncompressed WAV file and then encoded it into FLAC using the following command from the command line:

time flac $TESTSONG.wav –compression-level-X -o flacX.flac

This particular command will show the time to encode. All you need to do is substitute X for the compression level number (0 to 8 level compression).

Here are the system specs:

system specs for flac file test

Test Parameters:

  • Level: The FLAC compression level used
  • Encode (sec): The time it took to encode the song
  • Size (MB): The size of the resulting FLAC file
  • Encode Time (vs FLAC 0): The additional time required to encode as compared to FLAC 0 (in seconds)

The tables below show the comparisons of the two songs and the resulting performance after the complete process:

FLAC LevelEncode Time (sec)Size (MB)Encode Time (vs FLAC 0)
FLAC 03.836165.70.00
FLAC 13.924163.40.088
FLAC 24.267161.80.343
FLAC 35.743154.61.476
FLAC 46.836151.31.093
FLAC 59.734150.92.898
FLAC 69.836149.30.102
FLAC 717.364149.17.528
FLAC 822.634148.95.270

From the above, we notice the following:

  1. The best FLAC compression level with the best trade-off between file size and additional encoding time is FLAC 3, 4, or 5.
  2. FLAC 0 to 2 encodes very fast, but the file sizes are quite large.
  3. FLAC 6 to 8 takes a long time to encode, but the file sizes are very small.
  4. The difference between FLAC 0 and FLAC 3 in terms of size is very small. As such, you could rip your music in FLAC 0 if you have space. Let’s say you have 100 hours of music that will consume 


Should I Use A High or Low FLAC Compression?

Firstly, any FLAC compression level you choose, from FLAC 0 to 8 will save you a lot of space. However, you may not want to use a high FLAC compression level to compress say your music.

This is because when music files are compressed, they must be decompressed on the fly during playback.

At higher compression levels, your PC or music player must do more work to decompress the file. If you are on a mobile phone, for example, this means less battery life. 

Should I Use Mid-Level or High-Level FLAC Compression?

The difference between mid-level and high-level compression e.g. FLAC 5 vs FLAC 8 is that the higher levels will take much longer to compress.

FLAC 8 will typically take 3 times as long to compress a song as FLAC 5, however, the difference in file size will be negligible. 

FLAC compression levels considering encoding and decoding time

As such, it comes down to the compromise you are willing to make. In addition to taking longer to compress, higher-level compression FLAC files will also take longer to decode at playback.

Why Should You Use FLAC 3 to 5 For Compressing Music?

FLAC 5 is the default compression level for a good reason. This level of compression is the optimal balance between file size reduction and playback performance.

However, anywhere between FLAC 3 to 5 is normally a good compromise as indicated by the test above.

What Level of FLAC Compression is Best?

Compression levels in FLAC can be confusing and they often come up when you’re trying to decide what bitrate of audio files to use for your music collection.

Opinions vary, but the default FLAC compression level is 5. This is where a balance between file size reduction and performance is struck.

Does FLAC Compression Level Matter?

Yes. The file’s encoding level influences the amount of file size reduction and the time it takes to reduce it.

Consider FLAC to be a kind of zip for WAV files. It reduces the size of files, not the audio within them.

What is 24-bit FLAC?

24 Bit FLAC is a high-quality lossless compression format that allows you to save disk space and maintain great sound quality.

The difference between 24-bit uncompressed music files and the same song in 16-bit or 32-bit formats can be staggering.

So, it’s worth converting all your songs for personal use!

Some simple ways of doing this include ripping CDs as 24-bit WAVs, using an app like Decibel (free) on iOS to rip individual tracks from iTunes, or using macOS apps such as XLD and Audirvana.

You’ll need a modern iPhone/iPad with Lightning connectors if you want to take advantage of FLAC compatibility out of the box.

Is FLAC Better than 320 Kbps?

Absolutely! FLAC is better than 320 Kbps because it’s lossless, which makes it technically better.

The question is whether or not you’ll notice the difference between raw audio or FLAC and 192-320 Kbps MP3.


Your choice of FLAC compression level should depend on your intended use. If you have a lot of space or you are archiving, you can use a low compression level like  FLAC 0. However, if you are going to be playing your music on a mobile device with limited space and processing power. go for a mid-level compression where it doesn’t require a lot of processing power to decode, but the file sizes aren’t large. In this case, FLAC 3 to 5 should be OK. FLAC 6 to 8 are really for persons who have the processing power to easily decode these files on the fly but are keen on saving space. 

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Norvan Martin is the founder of BoomSpeaker.com. He is a professional Electronics Engineer and is passionate about home theater systems and AV electronics. BoomSpeaker was created as an online hub to share his knowledge and experiences as it relates to home theaters and home audio electronics. My email: [email protected]  Connect on Pinterest and Linkedin