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Mono fold-down · Channel swap · No upload

Stereo to Mono without the guesswork

A phone speaker, a small PA and most voice assistants play one channel. If the important part of a recording lives only on one side, it disappears there. Fold it down properly and hear what the room will hear.

Short answerLast edited October 31, 2026

The Stereo to Mono Converter folds a stereo file into one channel, keeps the left or right channel only, or swaps the two. Folding is done by adding the channels and halving the level, so two identical channels keep the same loudness.

Two ears, one signal

Stereo stores a left and a right channel. Mono stores one. Folding down is not deleting a side — it is combining both, and that combination is where phase problems become audible.

LRWhat each ear receives
Stereo field
−1 · out of phase+1 · identical
Correlation +0.42
Mono uses (L + R) ÷ 2, so nothing is lost and nothing is doubled.

Choose the output in three steps

1

Drop the file

The tool reads the channel count and the length before you choose anything.

2

Pick a mode

Mono for playback everywhere, left or right to rescue a broken recording, swap to fix a reversed cable.

3

Export

MP3 for delivery, WAV when the mono file goes back into an edit.

Five modes, five problems

Mono · average both sides

(L + R) ÷ 2. The safest fold-down: no channel is louder than the other, and the level cannot exceed the original peak. Use it for podcasts, voice notes and any content that will be played on a single speaker.

Mono · sum (louder)

L + R, limited to 0 dBFS. It keeps material that is out of phase in the audible range, but it can clip and it changes the level. Useful when one side is very quiet but the other is not silent.

Keep the left channel

Discards the right side. The rescue mode: a lavalier that only recorded on one side, a stereo cable with a broken tip, a file where the good take sits on the left.

Keep the right channel

The same, for the other side. Check both before exporting — one of them may contain a completely different performance.

Swap left and right

The file stays stereo, the channels exchange places. It fixes a reversed input pair, a miswired adapter or a video where the sound comes from the wrong side.

When each mode helps

SituationModeWhy
Phone speaker playbackMono averageOne speaker cannot reproduce two channels
Podcast delivered in monoMono averageConsistent on every app
One channel is silentKeep the good sideThe other side has no signal
Left and right reversedSwapFixes the image without a re-edit
A voice only on the leftKeep leftPreserves the take, drops the empty side
Phase-heavy synthMono sum, then checkExposes cancellation instead of hiding it

Channel questions, answered

Does converting to mono reduce quality?
It reduces the channel count, not the sample rate or bit depth. Information that differed between the sides is combined, which is the point. Nothing is uploaded and no compression is added unless you choose MP3.
Will the mono file be quieter?
Usually a little, because the two channels no longer add up. If it has to match other files, run it through the normalizer.
What is the difference between average and sum?
Average divides by two, so it is safe. Sum adds the channels without dividing, so it is louder and can clip. Use sum only when you know the material and the headroom.
Can I convert a mono file to stereo?
Not with this tool, and there is little to gain: a mono source has no stereo information to recover. If you need stereo width, use the chorus effect.
Which format should I choose?
MP3 for sharing, WAV for editing. A mono WAV is roughly half the size of the same stereo WAV.

What You Lose When You Fold Stereo to Mono

Stereo is a trick played on the ears: two channels, slightly different, create the impression of width and place. Mono is the honest version — one signal for every speaker. Folding one into the other is simple arithmetic, but the result depends entirely on how the two channels relate.

The arithmetic

The average fold-down is (L + R) ÷ 2. It keeps the level predictable and cannot clip. The sum is L + R; it is 6 dB louder when both sides carry the same signal, and it clips easily. Most of the time, average is the right choice. Sum is a diagnostic tool or a rescue for very quiet material.

Phase, the invisible problem

If a sound arrives at both channels with the same polarity, it adds. If it arrives with opposite polarity, it cancels. A wide synth pad can survive stereo and vanish in mono because its sides are deliberately out of phase. Nothing is broken; the mix was simply never checked in mono.

This is why broadcasters and podcast hosts ask for mono compatibility. A large part of the audience listens on one speaker, and the platform may fold the file down before it reaches them.

When one channel is enough

Sometimes the stereo file is not really stereo. A lavalier recorded to the left input only, a camera with a broken right channel, an interview where each speaker was panned hard to one side. Keeping the good channel is cleaner than averaging a signal with silence, which halves the level and doubles the noise floor.

Swapping is a repair, not an effect

If a voice seems to come from the wrong side, or a stereo recording feels mirrored, swap the channels. It is the cheapest fix for a reversed cable or a miswired adapter, and it preserves the stereo image instead of flattening it.

Mono in a stereo world

Do not delete the stereo master. Keep it for music platforms and headphones, and use the mono version for phone-first delivery, voice assistants, PA systems and anywhere the listener has one speaker. The two files serve different rooms.

If the mono version needs to match the loudness of the stereo one, finish with the normalizer. And if the mono version sounds thin, the problem is in the mix, not in the converter.

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Quick facts

  1. Summing stereo to mono is (L+R)/2, so two identical channels give the same level rather than double the level.
  2. A mono file is half the size of the same audio in stereo, because only one channel is stored.
  3. If the two channels are out of phase, summing them can cancel the voice almost completely — that is why a stereo test is worth a listen before publishing.W3C
  4. At 44.1 kHz the highest frequency a file can contain is 22.05 kHz, just above the hearing range of an adult.W3C
  5. Raising the sample rate of an existing file adds no detail: the missing high frequencies are not in the recording.W3C

Questions people ask

When should I convert stereo to mono?
Convert to mono for voice recordings, phone calls and podcasts, where stereo adds no information. It also halves the file size and makes the sound consistent on mono speakers.
Will converting to mono lose the sound of one channel?
Folding to mono keeps the content of both channels, combined into one. If one channel holds a sound the other lacks, that sound is kept at half level. Keep only the left or right channel if you need one side alone.
Why does a stereo file sound quiet in mono?
Sounds that appear only in one channel are kept, but sounds that are out of phase between the channels can cancel when they are summed. This is why stereo recordings sometimes sound thinner after folding.

What this page is about

  • Stereo and mono

    Two channels carrying a left and a right signal, against one channel that both speakers play; summing them halves the data.

  • Sample rate

    How many times per second an audio signal is measured; by the Nyquist theorem it can represent frequencies up to half that rate.

  • Web Audio API

    The W3C API that builds an audio graph in the browser and can render it faster than real time with an OfflineAudioContext.

Official sources cited on this page

  1. Web Audio APIW3C

Continue with the same file

Each of these opens what the tool above produces. Use “Use in another tool” under the result to carry the file over — it moves from tab to tab inside your browser, never to a server.

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Switched-off tools are not listed here: only what works right now.

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