Convert MP3 to M4A: Free Online Converter
Convert MPEG Audio Layer 3 to MPEG-4 Audio online for free. Fast, secure audio conversion with no watermarks or registration.
MP3に対応
アップロードすることで、これらのファイルの権利を有していること、および利用規約に同意することを確認したものとみなされます。
変換設定: ファイルを追加すると調整できます
安全な転送
HTTPS暗号化アップロード
プライバシー優先
ゲストのファイルは約2時間で自動削除
登録不要
すぐに変換を開始
どこでも動作
あらゆるブラウザ、あらゆるデバイス
About MP3 files
MP3 is the classic lossy audio format and plays almost everywhere. M4A is AAC audio in an MP4 container, the native format of Apple Music, iTunes and iPhone ringtone tools.
People convert MP3 to M4A to use a song in Apple apps that expect M4A, to make an iPhone ringtone, or to keep a library in one Apple-friendly format.
How we convert MP3 to M4A
- Encoder
- AAC at 192 kbps inside an M4A container.
- Cover art and tags
- Cover art can carry over, and title, artist, album, year and genre can be edited.
- Trim
- Set a start time and a length, which is useful for ringtones.
- Fade
- Fade in and fade out options smooth the start and end of a clip.
Common problems and fixes
You want a ringtone, but the song is too long.
Use trim to keep a short section, and add a short fade out so it does not cut off hard.
The M4A is larger than the MP3.
If the MP3 was 128 kbps, the 192 kbps default makes a bigger file. Choose a lower bitrate to match the source.
Music apps show no artwork.
Check that the MP3 has embedded cover art. If not, the M4A will have none either.
MP3 から M4A への設定
- エンジン
- メディア
- 設定
- 調整できる設定: 11
- Trim Start
- Trim End
- Volume
- Fade In
- Fade Out
- Bitrate
- Sample Rate
- Channels
- Audio Channels
- Reverse Audio
- Strip Metadata
MP3からM4Aへの変換について
M4A is the file extension for MPEG-4 Audio: essentially an MP4 container holding only audio, typically encoded with AAC. Apple standardized M4A as the audio format for iTunes, Apple Music, and all Apple devices. Every song purchased from the iTunes Store since 2003 has been an M4A file. Converting MP3 to M4A modernizes your audio library to the format that the Apple ecosystem is built around, while also benefiting from AAC's superior compression efficiency compared to MP3.
MP3 was revolutionary when the Fraunhofer Institute released it in 1993, but its psychoacoustic model is a generation behind AAC. MP3's modified discrete cosine transform operates on fixed-size blocks of 576 samples, while AAC uses flexible window sizes from 128 to 2048 samples, allowing it to react more precisely to transients in music. The result: AAC in M4A sounds measurably better than MP3 at every bitrate.
MP3をM4Aに変換する理由
M4A is the native audio format for the Apple ecosystem — Apple Music, iTunes, iPhone, iPad, Mac, HomePod, AirPods, and Apple TV all treat M4A as the default. While these devices play MP3 too, M4A receives preferential treatment for metadata handling, gapless playback, chapter markers, and audio processing optimizations.
Beyond Apple, M4A/AAC has become the de facto standard for modern audio distribution. YouTube encodes audio in AAC. Spotify uses AAC for its web player. Android supports M4A natively. Web browsers universally support AAC via HTML5 audio. By converting your MP3 collection to M4A, you are moving from the 1993 standard to the modern one that powers contemporary audio delivery.
主な活用例
- Modernize an MP3 music library for Apple Music, iTunes, and iCloud Music Library
- Get better audio quality at the same file size by switching from MP3 to AAC encoding
- Enable gapless playback for live albums and DJ mixes across Apple devices
- Prepare audio for podcast distribution where AAC is the recommended codec
- Create a universally compatible library that works on Apple, Android, and web browsers
- Fix metadata and cover art inconsistencies by moving from MP3 ID3 tags to M4A atoms
仕組み
Our media engine decodes the MP3 source and re-encodes using the AAC-LC codec into an M4A (MPEG-4 Part 14) container. Default settings produce 192 kbps AAC at the sample rate of the source, though bitrate is configurable. The M4A container supports iTunes-compatible metadata atoms including title, artist, album, cover art, track/disc numbers, lyrics, gapless playback flags, and chapter markers. Metadata from MP3 ID3 tags is automatically mapped to M4A atoms during conversion.
品質とパフォーマンス
AAC at 128 kbps in M4A provides perceptual quality equivalent to approximately 160 kbps MP3. At 256 kbps AAC, quality exceeds 320 kbps MP3 in independent listening tests. The lossy-to-lossy transcoding introduces a theoretical generation loss, but at 128 kbps AAC and above from typical MP3 sources, the difference is inaudible. For the best results, use the same or higher bitrate as the source MP3.
デバイス互換性
| Device | MP3 | M4A |
|---|---|---|
| Windows PC | Native | Partial |
| macOS | Partial | Native |
| iPhone/iPad | Partial | Native |
| Android | Native | Partial |
| Linux | Partial | Partial |
| Web Browser | Native | No |
プラットフォーム別の推奨設定
Spotify
Resolution: N/A
Bitrate: 320 kbps
OGG Vorbis preferred
Apple Music
Resolution: N/A
Bitrate: 256 kbps
AAC format required
SoundCloud
Resolution: N/A
Bitrate: 128 kbps
Lossless FLAC/WAV for best quality
Podcast
Resolution: N/A
Bitrate: 128 kbps
MP3 mono for spoken word
最良の結果を得るためのヒント
- 1Use 256 kbps AAC to match Apple's iTunes Plus quality standard for maximum fidelity
- 2M4A metadata atoms are more reliable than MP3 ID3 tags for cover art on Apple devices
- 3Gapless playback metadata in M4A ensures seamless transitions between live album tracks
- 4Batch convert your entire library — the process is fast and metadata transfers automatically
- 5128 kbps AAC sounds equivalent to 160 kbps MP3, giving you better quality at the same size
関連する変換
MP3 to M4A conversion is the most impactful audio format upgrade you can make. M4A with AAC provides better quality, richer metadata, and universal device support — modernizing your audio library from the 1993 standard to the one that powers Apple Music, YouTube, and every modern audio platform.
MP3とM4Aの比較
| 特徴 | MP3 | M4A |
|---|---|---|
| 正式名称 | MPEG Audio Layer III | MPEG-4 Audio |
| 拡張子 | .mp3 | .m4a |