Audacity's multichannel ceiling is not one number — it is set by the format you export to. The Advanced Mixing Options page states the two headline figures directly: "32 output channels (WAV, AIFF or OGG)" and "8 output channels (FLAC)."
Past those two, it gets messier: the manual's own format comparison table and the footnote directly beneath it do not agree about M4A.
The channel limits, at a glance
These are the values in the "Channels" column of the Export Formats page, reproduced as written, with the manual's own footnote markers kept intact:
| Format | Channels | What the page says about it |
|---|---|---|
| WAV 16-bit PCM | 32 | Matches the 32-channel figure on the Advanced Mixing Options page |
| AIFF 16-bit PCM | 32 | Same |
| Ogg Vorbis | 32 | Same |
| FLAC 16-bit | 8 | Advanced Mixing Options also gives 8 |
| M4A (AAC) | 32(2) | Footnote (2) contradicts the 32 — see below |
| WMA v2 | 8(3) | Footnote (3) caps it at 2 channels via the WMA (version 2) Files (FFmpeg) choice or (external program) |
| AC3 | 7 | The Errors FAQ says "Six channels is the maximum possible for AC3." |
| MP2 | 2 | — |
| MP3 | 2 | — |
| GSM 6.10 WAV | 1 | — |
Two rows there are worth slowing down on.
M4A is the big one. The table cell says 32. Footnote (2) on the same page says something quite different: "More than 2 channels output is not supported with the recommended FFmpeg 2.2.2 library, unless you export using (external program) with a command that tells Audacity to explicitly use the native FFmpeg encoder. This produces maximum 6 channels. For up to 8 channels, point the same command to the latest FFmpeg-git."
So the cell says 32, while the note attached to it describes a practical ceiling of 2, 6 or 8 depending on which encoder you reach. Read only the table and you will plan a 5.1 AAC export that stops before it starts. The Errors FAQ shows what that failure looks like: "Error 0x15002 occurs if you export more than a 2-channel M4A file (such as a 5.1 surround sound file), using the "M4A (AAC) Files (FFmpeg)" export choice."
Take the footnote as the operative version — it is the more specific of the two. The Errors FAQ also tells you to "choose (external program) and specify a command that tells Audacity to explicitly use the native FFmpeg AAC encoder" to get "up to 8 channels", but omits the FFmpeg-git condition that the footnote attaches to the 8-channel figure.
AC3 is the smaller one. The table lists 7 channels; the Errors FAQ says "Error 0x15003 occurs if you export more than a 6-channel AC3 file. Six channels is the maximum possible for AC3."
Where the multichannel switch actually lives
This is the second place people get stuck, and it is a documentation mismatch rather than a fault in your project.
The Mixing page sends you to preferences: "Although Audacity by default exports files as either two channel stereo or single channel mono (if exporting unpanned mono tracks), you can also export multi-channel files having more than two channels, such as a 5:1 file. To enable this, choose "Use custom mix" in the Import / Export Preferences." The Export Formats page repeats the same instruction.
The Import / Export Preferences page itself lists four groups of settings — Exported Label Style, Exported Allegro (.gro) file saves time as, Music Imports, and the behaviour when importing a music loop into an empty project. No "Use custom mix" among them.
Go by the Export Audio dialog instead. Its own page describes the control in place: "Custom mapping: use this to export multi-channel (surround sound) files or to make customized assignments between Audacity tracks and the channels in the exported file." And: "Selecting this and clicking on the Configure button causes the Advanced Mixing Options dialog to appear."
That is the route: File > Export Audio, set Channels to Custom mapping, click Configure. The dialog that opens is the one carrying the 32-channel and 8-channel limits quoted above.
What to do when you hit the ceiling
If the format is the problem, change the format. WAV, AIFF and OGG all carry the 32-channel figure, so a surround mix that will not fit into FLAC or AAC will fit into any of those three. The trade is size: WAV and AIFF are capped at 4 GB — the manual calls this "a general restriction and not an Audacity one" — and a many-channel file reaches that faster than a stereo one.
For genuinely large multichannel work, the Other uncompressed files exporter is the documented escape hatch: "RAW, RF64 or CAF (Apple's Core Audio Format) headers (with PCM encoding in all three cases) may be used if extremely large files similar to WAV or AIFF are required. The RF64 and CAF size limit is about 16 exabytes (effectively unlimited, as there are no disks of that size), making it suitable for very long multi-channel files." You reach it through File > Export Audio and picking Other uncompressed files from the Format dropdown.
If the source material is stuck inside a video container, get the audio out before you start mixing. This runs in your browser rather than sending the file anywhere:
Try it right here
Runs in your browser. Your file is not uploaded anywhere.
It pulls the audio out of a video file to WAV without a lossy re-encode — check the track count Audacity shows after importing, since that is what you will be mapping. To shrink the result afterwards, WAV to MP3 handles the lossy step; the full set is on the tools page.
Gotchas the channel table does not warn you about
The Advanced Mixing Options page carries four constraints that catch people out well after they have chosen a format.
- Split in parts cannot do multichannel at all. Verbatim: "Currently there is no support for exporting multi-channel files when using Split in parts (to export multiple audio files) from the Export Audio dialog." If your workflow is one file per label or per track, multichannel is off the table for that pass.
- You cannot audition the result in Audacity. "There is no support at the moment for multi-channel playback of audio in Audacity - playback of a multi-channel file in Audacity will always be mixed down to stereo." The same sentence continues:
Tracks > Mix > Mix and RenderandTracks > Mix > Mix and Render to New Track"only mix down to mono or stereo." - Channel order is not assigned for you. "Audacity does not perform mapping of the channels in exported files to specific playback channels." The page offers an observation rather than a rule: "In addition, 5.1 files in OGG and AC3 formats are often FL, FC, FR, SL, SR, LFE." And then the caveat that matters most: "There is no guarantee that a sound device or any particular file will follow recommended channel mapping for the format."
- Stereo is the default even when it makes no sense. The Export Audio page says of the Channels setting: "Stereo: stereo pair with left and right channels - this is the default setting even if you only have mono tracks for exporting." A multichannel export that came out as stereo usually means Custom mapping was never selected.
For the AAC route specifically, the manual's own external-program example is ffmpeg -i - -strict experimental -c:a aac -b:a 240k "%f", and it notes that "The native encoder is required to export more than stereo, up to a maximum of 6 channels." If AAC bit rates are also misbehaving for you, that is a separate documented issue — see why Audacity ignores your AAC bit rate. More format ceilings are collected under limits.
FAQ
How many channels can Audacity export? It depends on the format. The Advanced Mixing Options page gives "32 output channels (WAV, AIFF or OGG)" and "8 output channels (FLAC)". The format comparison table lists 32 for WAV, AIFF and Ogg Vorbis, 8 for FLAC, 7 for AC3, and 2 for MP3 and MP2.
Can Audacity export 5.1 surround to M4A or AAC? Not with the standard export choice. The manual's footnote says more than 2 channels "is not supported with the recommended FFmpeg 2.2.2 library" unless you use (external program) with the native FFmpeg encoder, which "produces maximum 6 channels" — 8 requires pointing the same command at the latest FFmpeg-git. Trying it the normal way produces Error 0x15002.
Why does my multichannel file play back as stereo in Audacity? Because that is documented behaviour, not a failed export: "playback of a multi-channel file in Audacity will always be mixed down to stereo." Check the file in a player that supports the channel layout instead.
Where is the "Use custom mix" setting? Two pages send you to Import / Export Preferences for it, but that page lists only four other settings. Use Custom mapping in the Export Audio dialog, then Configure, which opens Advanced Mixing Options.
Can I export multiple multichannel files in one pass? No — "there is no support for exporting multi-channel files when using Split in parts (to export multiple audio files) from the Export Audio dialog."
All quotations are from the Audacity Manual pages on Advanced Mixing Options, Export Formats supported by Audacity, the Export Audio Dialog, Mixing, and FAQ: Errors, checked 16 September 2026. Where the manual gives two different figures for the same thing, both are quoted above rather than reconciled. For anything not quoted here — FFmpeg version requirements and installation in particular — check the official documentation.
