Free tools for your next audio edit
Make a new MP3 from a short recording at a chosen bitrate. Compare its actual byte size with your original and your size limit, then listen before downloading. Your audio stays in this browser; a new encode is not always smaller.
Choose WAV to create an MP3 delivery copy, or MP3 for a new encode. Preview and compare the actual file size before downloading.
A comparison only: this does not automatically choose a bitrate or guarantee acceptance by another service. Check that destination's actual rules.
Your audio stays in this browser. No trimming, fades, normalization, mono downmix, or noise removal is applied. Keep your original; this tool does not promise a smaller file at every bitrate.
Encode, compare, then listen
Keep the original file. Work from it for each comparison instead of repeatedly compressing an exported MP3.
Open a mono or stereo MP3 or WAV up to 50 MiB and five minutes. A WAV container can hold codecs a browser cannot decode; use standard PCM WAV or a supported MP3 if the file fails to open. Video and other audio extensions are not accepted here.
Select 64, 96, 128, 192, or 320 kbps. Enter the destination's size limit and choose MB or MiB. This limit is a comparison, not an automatic bitrate setting. Start the MP3 export; longer files can take more time on a phone or slower device.
Read the original and exported sizes, the change in bytes, and whether the new file meets your selected limit. Alternate between the original and MP3 players at a similar listening volume. Download only if the result suits the task. A larger export remains available, with its size increase reported.
A compressed delivery from your working file
Choose your WAV above, select an MP3 bitrate, and prepare the export. This is the same working local encoder as the file-size workflow: there is no second upload, account, or conversion queue. Preview the resulting MP3 and download that exact file. Choose 128, 192, or 320 kbps when those settings match your delivery needs; 64 and 96 kbps are available for a smaller-size comparison.
At 320 kbps, a one-minute MP3 payload is approximately 2,400,000 bytes. A one-minute 48 kHz, 16-bit stereo PCM payload is 11,520,000 bytes. Headers, padding, and source metadata affect actual file sizes, so use the displayed export comparison rather than treating those numbers as an exact download size or a quality score.
WAV can contain different encodings. The browser must be able to decode the selected file; this tool prepares 16-bit samples at 48 kHz before the MP3 encode. It does not preserve source bit depth, tags, artwork, or compressed frames. MP3 may add delay or padding and change the decoded peaks. Keep the original WAV for further editing and precise timeline placement.
For a file you already received as MP3, select it only when you deliberately want a new encode. Choosing 320 kbps for a low-bitrate source can make it larger without restoring missing detail. Read the MP3 and WAV editing guide before replacing a useful original with a delivery copy.
Fewer bits per second, a different recording
For a fixed-bitrate encoded stream, duration multiplied by bitrate gives an approximate payload size. For example, five minutes at 128 kbps gives 4,800,000 bytes of payload; at 64 kbps it gives 2,400,000 bytes. Framing and padding can change the actual output. These are storage calculations, not quality recommendations or a guaranteed compression ratio.
Estimated MP3 payload bytes = seconds × kbps × 1,000 ÷ 8The audio file size and bitrate calculator can work backward from your duration and budget. This tool completes the next step: it encodes an actual file and checks that file's byte size. A payload estimate under a limit is not proof that the final file fits.
One decimal MB is 1,000,000 bytes. One binary MiB is 1,048,576 bytes. The same displayed limit number therefore represents different budgets. This comparison does not account for an email service's message encoding or change any destination's upload policies.
Compare the tradeoff
Keep the original and download the chosen MP3. Check the saved file in its destination as well. Intelligible words, natural breaths, percussion, and musical tails matter more than a large percentage reduction alone.
Try a lower available bitrate from the original, or shorten the recording with the free audio trimmer. If every passage is required and a lower rate damages it, choose another permitted delivery method rather than discarding wanted content silently.
Keep the original. An already compressed source may use fewer bits than the selected output rate, and a new MP3 encode cannot restore lost detail. The displayed comparison reports actual bytes; it does not assume that every export saves space.
File size is separate from loudness
An audio engineer's compressor controls level dynamics with settings such as threshold, ratio, attack, and release. This utility has none of those controls. It re-encodes the complete recording at a chosen MP3 bitrate without deliberately changing gain, trimming, fading, downmixing, or separating noise.
A mono source remains mono; stereo remains stereo. Samples are prepared as 16-bit PCM before encoding, with rounding and clipping to that range. The browser decodes at 48 kHz, which can resample the source. At low bitrates, the MP3 encoder can choose a lower output sample rate as well. Lossy encoding can alter decoded levels and samples, so an unchanged gain setting does not promise identical peaks or loudness.
If measurement is needed, use the LUFS loudness meter on the actual chosen file. The peak normalizer is a separate utility for a sample-peak target. Neither measurement nor normalization establishes that the file meets a storage limit.
Keep an editable original
Converting a WAV to MP3 changes the format and discards information. Re-encoding an MP3 adds another lossy step. The tool does not copy tags or artwork, repair clipping, restore missing detail, or create a lossless archive. Its original and exported players allow a listening comparison; neither starts automatically.
MP3 can add encoder delay or padding. Keep a WAV working copy when precise placement against video or another track matters, and check the final timeline rather than treating the planned decoded duration as sample-accurate MP3 delivery. The MP3 and WAV editing guide explains choosing a source, a working copy, and a final export.
All processing here uses your browser and the separately served encoder. No audio upload, account, credit, or AI separation job is started. Save the chosen result before leaving; the tool does not store your recording for a later session.
Compare bitrate and duration, work through a 1 MB budget, and choose what to change when a complete recording cannot fit.
MP3 encoder credits
The MP3 download uses lamejs 1.2.1 by Alex Zhukov, a JavaScript port of the LAME MP3 encoder. Its unmodified script is served separately. See the attribution and source notes, upstream license notice, LGPL-3.0 and GPL-3.0 texts, and complete upstream source package.
A few useful answers
Open a supported MP3 or WAV up to 50 MiB and five minutes, select 64, 96, 128, 192, or 320 kbps, and encode the new MP3. The tool compares actual original and exported byte sizes. Try a lower rate if needed, but listen for lost detail and keep the original.
Encoding, previewing, and downloading are free, with no account or audio upload. The browser decodes the file and a local worker encodes MP3. Download the result before leaving or reloading. The separate AI isolation service has its own account and credit requirements.
You can enter a comparison limit in MB or MiB and check the actual export against it. This does not automatically choose a bitrate or guarantee a fit. Lower the selected bitrate or prepare a shorter excerpt when the result exceeds the limit. Check the destination's actual rules too.
No. MP3 is lossy, and this tool decodes and re-encodes rather than copying existing MP3 frames. A higher bitrate cannot restore missing information. Keep a lossless working original when available and avoid repeatedly re-encoding an already compressed result.
The source may already use a lower or variable bitrate, or be very short. Codec framing, padding, and source metadata also affect the comparison. The tool reports a larger export rather than claiming savings. Keep the original if the only goal is smaller storage.
Yes. Open a supported short mono or stereo WAV, select 320 kbps, and prepare the MP3. Preview the actual export and check its byte size before downloading. The conversion is local and free, but MP3 remains lossy. A higher output bitrate cannot recover detail missing from the source or guarantee that an already compressed input becomes smaller.
You can convert a supported mono or stereo WAV to a new MP3, which changes the format and discards information. It does not make a lossless smaller WAV or FLAC. The decoded channel count is retained. The browser decodes at 48 kHz, but the MP3 encoder can lower the output sample rate at lower bitrates. Original tags and artwork are not copied.
No. This tool changes encoded file size by choosing an MP3 bitrate. It has no threshold, ratio, attack, release, or loudness target. It does not deliberately normalize peaks, remove noise, trim silence, or make a recording more even in level.
The complete decoded recording is passed to the encoder, but browser decoding can resample and MP3 encoding can add delay or padding. Keep WAV for a working copy when precise timeline placement matters, and check sync before using a compressed export with video.
After preparing your audio