MP3 Bitrate Calculator
Use this audio file size calculator to calculate file size from bitrate and duration, or find the required bitrate to hit a target file size. Whether you need a quick MP3 size estimator or want to compare lossless versus lossy sizes across formats, this tool supports lossy formats (MP3, AAC, Opus, Vorbis) with format-aware quality assessment, plus lossless (FLAC, WAV) computed from PCM parameters.
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3-Minute Stereo File Size by Format & Bitrate
| Format @ bitrate | Bitrate | 3 min file | 1 hour file |
|---|---|---|---|
| MP3 64 kbps | 64 kbps | ~1.44 MB | ~28.8 MB |
| MP3 96 kbps | 96 kbps | ~2.16 MB | ~43.2 MB |
| MP3 128 kbps | 128 kbps | ~2.88 MB | ~57.6 MB |
| MP3 192 kbps | 192 kbps | ~4.32 MB | ~86.4 MB |
| MP3 256 kbps | 256 kbps | ~5.76 MB | ~115.2 MB |
| MP3 320 kbps (max) | 320 kbps | ~7.20 MB | ~144.0 MB |
| AAC 128 kbps (≈ MP3 192) | 128 kbps | ~2.88 MB | ~57.6 MB |
| AAC 256 kbps | 256 kbps | ~5.76 MB | ~115.2 MB |
| Opus 96 kbps (≈ MP3 192) | 96 kbps | ~2.16 MB | ~43.2 MB |
| Opus 128 kbps | 128 kbps | ~2.88 MB | ~57.6 MB |
| FLAC 44.1k/16-bit stereo | ~847 kbps | ~19.05 MB | ~381.0 MB |
| FLAC 96k/24-bit stereo | ~2,765 kbps | ~62.21 MB | ~1.24 GB |
| WAV 44.1k/16-bit stereo | 1,411 kbps | ~31.75 MB | ~635.0 MB |
| WAV 96k/24-bit stereo | 4,608 kbps | ~103.7 MB | ~2.07 GB |
About Audio Bitrate & File Size
Bitrate is how many bits of audio data are stored per second, expressed in kilobits per second (kbps) or megabits per second (Mbps). File size scales linearly with bitrate × duration. The conversion is direct: bytes = (bitrate_kbps × 1000 / 8) × duration_sec. Note that bitrate only tells you data throughput — it does not directly describe the audio’s sample rate or bit depth, which are the parameters that define PCM fidelity. To explore how those relate to file size for WAV and FLAC files, see the sample rate converter and bit depth calculator.
Lossy vs lossless
Lossy formats (MP3, AAC, Opus, Vorbis) discard psychoacoustically-imperceptible information — exploiting auditory masking and other perceptual effects — to reach low bitrates with subjective quality near the original. The AAC file size at a given bitrate is identical to MP3 at the same bitrate, but AAC sounds noticeably better because of its more efficient codec. Lossless formats (FLAC, ALAC, APE) use entropy coding to compress the exact PCM signal — FLAC compression typically achieves 50–70% of WAV size with bit-perfect reconstruction. Uncompressed PCM (WAV, AIFF) stores raw samples — biggest files but trivial to process and universally compatible.
CBR vs VBR encoding
Most bitrate presets above assume constant bitrate (CBR) encoding, where every second of audio uses the same number of bits. Variable bitrate (VBR) allocates more bits to complex passages (busy mix, transients) and fewer to simple ones (silence, sustained tones), yielding smaller files at the same perceived quality. An MP3 encoded at VBR V2 (~190 kbps average) typically sounds better than CBR 192 kbps at the same average file size. File-size estimates for VBR are averages; actual size varies with content.
Format efficiency: AAC and Opus beat MP3
At equivalent perceptual quality, AAC needs about 70% of MP3’s bitrate, and Opus about 50–60% of MP3’s. So AAC 128 kbps roughly matches MP3 192 kbps, and Opus 96 kbps matches MP3 192. For new projects, Opus is technically the best lossy choice; AAC remains the de facto streaming standard (Apple Music, YouTube, Spotify use AAC or Opus); MP3 persists for backward compatibility with legacy devices.
Picking a target bitrate
For background music or podcasts: 96–128 kbps (MP3) is fine. For careful listening: 192–256 kbps. For audiophile-grade or master copies: lossless. The 320 kbps MP3 ceiling is “transparent” for most listeners — anything above adds bytes with diminishing perceptual return. Game audio and video embeds often use OGG Vorbis or Opus at 128–192 kbps for a good size-quality trade-off.