Audacity Default MP3 Bitrate: 128 or 170-210 kbps?

Audacity's default MP3 export is not 128 kbps — the default is the Preset mode at quality "Standard", which the manual documents as 170 - 210 kbps VBR. The 128 kbps figure is real, but it is the default of a different bit rate mode, and it lives on a different page of the official manual.

If you searched this question and got two answers, that is not because the internet is sloppy. Audacity's own documentation gives two.

The two official figures, side by side

Sources: MP3 Export Options and FAQ: MP3 export problems.

You cannot settle this by checking which page is newer. Every page in the current manual carries the same footer line, "This version created on 2026-09-02", so there is no newer page to prefer.

Which figure applies to a fresh install

Go with the MP3 Export Options page. It is the dedicated page for the export dialog, and it states the same thing three separate times without contradicting itself:

• On the Bit Rate Mode control: "Preset: Default setting, this offers the various Quality settings recommended by the LAME developers for encoding music."
• On the quality presets: "Standard: Very good quality encoding. This is the default setting in Audacity."
• As a summary: "The default MP3 encoding options in Audacity are 170 - 210 kbps VBR (preset "Standard")."

Put together: Bit Rate Mode defaults to Preset, Quality defaults to Standard, and that combination is documented as a 170 - 210 kbps variable bit rate. It is a range rather than a number because the manual says so directly — "The bit rates are absolute for average and constant bit rate modes, but expressed as a range for the Variable and Preset modes (except for the Excessive preset)."

Where 128 kbps actually comes from

The same MP3 Export Options page does print 128 kbps — inside its description of Constant bit rate mode:

"The available bit rates are the same as for average bit rate - the default rate (128 kbps) gives you a known file size of about 1 MB per minute of mono or stereo audio."

So 128 kbps is the value the bit rate dropdown starts at once you switch to Constant, not the value a default export uses. That "about 1 MB per minute" figure belongs to 128 kbps CBR too — it is not a size estimate for the VBR Standard default. Audacity's format comparison table agrees and keeps the qualifier attached, listing MP3 at "1.0 (CBR)" MB per minute for both mono and stereo.

There is also a legitimate reason the FAQ's wording matches what some people see. The same sentence continues: Audacity "then remembers the last used bit rate if you change it." A copy of Audacity that someone once set to 128 kbps CBR keeps exporting at 128 kbps CBR. So "mine says 128" and "the manual says 170 - 210" can both be true on two machines.

What each bit rate mode actually sets

Two cross-references are worth knowing if you want a specific quality without hunting through presets. The manual maps the two scales onto each other: "Level 0 is comparable to the Extreme preset mentioned above, level 2 is comparable to Standard and level 4 to Medium presets." And it warns about the mono case explicitly — "For a mono track, the achieved bit rate for each setting will usually be below the range indicated above." Exporting a mono voice track at Standard will not land in 170 - 210 kbps.

On the presets themselves, the manual only publishes a hard number for two of the four. Excessive is "a constant bit rate of 320 kbps, which is equivalent to 2.4 MB per minute". Standard is the 170 - 210 kbps VBR default. For Extreme and Medium the manual gives quality descriptions but no kbps range, so check the official documentation rather than trusting the numbers that circulate on forums.

Changing it, and what else the dialog fixes for you

The route is File > Export Audio, then choosing MP3 from the Format dropdown menu. Two settings there surprise people:

• Sample rate has only three choices — the manual lists "32000 Hz", "44100 Hz - default setting" and "48000 Hz". This is unlike formats that simply follow your project rate.
• Stereo mode is not a choice at all: "The MP3 export will always use joint stereo for the exported audio file."

If your source is a lossless file and MP3 is only the delivery format, the cleanest workflow avoids the question entirely. The manual is blunt about why: "If you import an MP3 into Audacity, edit it then export it as an MP3, you will lose quality twice… So never do production work in MP3, instead work with a lossless format such as WAV, AIFF or FLAC and for final use then export to MP3." When the only step left is that final conversion, you do not need to reopen a project for it:

Try it right here

Runs in your browser. Your file is not uploaded anywhere.

Loading tool…

This runs in your browser tab — the file is read from disk and encoded locally, never uploaded. For the full set, see all Clapr tools, or WAV to MP3 directly.

Gotchas the default bitrate causes

Your exported MP3 came out bigger than the MP3 you imported. The FAQ names the cause: "this is because the bit rate you exported it at is higher than the bit rate of the original file." A 96 kbps podcast episode re-exported at the Standard default will grow. The same page also explains why matching the original rate is not a free fix — doing so degrades quality more than exporting higher, and "file merge tools might no longer be able to join the new MP3 to others that had the original bit rate". There is more on this in why your Audacity MP3 is larger than the original.

For spoken word, the default is the wrong pick. The manual says so in its own words: "For podcasts, "CBR" (Constant Bit Rate) is recommended, and not "VBR" (Variable Bit Rate)", and follows up that the 170 - 210 kbps VBR default, "while this is a good choice for stereo music, it is not generally recommended for Podcasts." Its published ladder is 64 kbps CBR mono for "reasonable quality for voice", 96 kbps CBR mono for "excellent quality for voice", 128 kbps CBR stereo where stereo is required, and 192 kbps CBR stereo for "very good quality".

On Linux, you may not get an MP3 option at all until LAME is installed. The manual states that the LAME library "is built-in with Audacity for Windows and Mac", and that "Linux users will still need to download and install the free and recommended LAME third-party encoder to export MP3 files from Audacity."

FAQ

What is Audacity's default MP3 bitrate? 170 - 210 kbps VBR, produced by the default Preset mode at quality Standard, per the MP3 Export Options page. A second page, the MP3 export problems FAQ, says Audacity "defaults to 128 kbps" — that figure matches the default of Constant mode.

Why does my Audacity show 128 kbps then? Either the Bit Rate Mode is set to Constant, or the setting was changed at some point: the manual says Audacity "remembers the last used bit rate if you change it."

Is 170 - 210 kbps VBR good enough for music? The manual calls Standard "Very good quality encoding" and "a good choice for stereo music". It adds that "For better than "very good" for music, you should really be using 256 kbps VBR", noting that is "Good for home use but not for streaming."

How big will a default MP3 export be per minute? The published "about 1 MB per minute" number applies to 128 kbps constant bit rate, not to the VBR default. Because VBR size depends on the audio, the manual notes that with VBR "the achieved size will vary depending on the content."

Does changing the bitrate fix the silence at the start of an MP3? No — that is separate, and the manual attributes it to encoder delay in the MP3 format itself. See MP3 silence at the start in Audacity.

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All figures quoted from the official Audacity Manual pages linked above, checked 16 September 2026. More specification write-ups in limits.