Bitrate is one of the most important concepts in digital audio—it directly affects file size, audio quality, and compatibility. Whether you're splitting podcasts, music files, or recordings, understanding bitrate helps you make informed decisions about quality and storage. This guide explains everything you need to know about audio bitrate.
What is Audio Bitrate?
Bitrate measures how much data is used to encode each second of audio. It's expressed in kilobits per second (kbps)—thousands of bits of data per second of audio.
For example, a 128 kbps MP3 uses 128,000 bits (16 kilobytes) of data for each second of audio. A 3-minute song at 128 kbps would be approximately 2.8 MB.
Bitrate vs Quality
Higher bitrates allow more audio detail to be preserved, but there's a point of diminishing returns—most people can't hear the difference above certain thresholds.
MP3 Bitrate Quality Scale
Bitrate and File Size
There's a direct relationship between bitrate and file size. You can calculate approximate file size with this formula:
File Size Calculator
Example: 128 kbps × 180 seconds ÷ 8,000 = 2.88 MB for a 3-minute song
| Bitrate | 1 Minute | 5 Minutes | 30 Minutes | 1 Hour |
|---|---|---|---|---|
| 64 kbps | 0.47 MB | 2.34 MB | 14.1 MB | 28.1 MB |
| 128 kbps | 0.94 MB | 4.69 MB | 28.1 MB | 56.3 MB |
| 192 kbps | 1.41 MB | 7.03 MB | 42.2 MB | 84.4 MB |
| 256 kbps | 1.88 MB | 9.38 MB | 56.3 MB | 112.5 MB |
| 320 kbps | 2.34 MB | 11.72 MB | 70.3 MB | 140.6 MB |
CBR vs VBR: Encoding Methods
Audio can be encoded with either constant or variable bitrate. Each has advantages:
CBR (Constant Bitrate)
- Same bitrate throughout entire file
- Predictable file sizes
- Better streaming compatibility
- May waste bits on simple passages
- Easier to seek/split precisely
VBR (Variable Bitrate)
- Bitrate varies based on complexity
- Better quality at same average size
- More efficient encoding
- File sizes less predictable
- Harder to calculate exact timing
How VBR Works
Variable bitrate encoding analyzes the audio and allocates more bits to complex passages (loud music, multiple instruments) and fewer bits to simple passages (silence, sustained notes). This achieves better quality per byte.
For example, a VBR file might use 320 kbps during a complex orchestral crescendo but only 64 kbps during a quiet fade-out. The average bitrate might be 192 kbps, with quality exceeding a CBR file of the same average size.
Bitrate by Audio Format
Different audio formats use bitrate differently:
| Format | Type | Typical Bitrate Range | Notes |
|---|---|---|---|
| MP3 | Lossy | 32-320 kbps | Most common format; 320 kbps maximum |
| AAC | Lossy | 64-320 kbps | Better than MP3 at same bitrate |
| OGG Vorbis | Lossy | 45-500 kbps | Flexible quality levels |
| WAV | Uncompressed | ~1,411 kbps (CD) | Fixed rate based on sample rate/depth |
| FLAC | Lossless | ~600-1,200 kbps | VBR by nature; varies with content |
Uncompressed Audio Bitrate
For uncompressed formats like WAV, bitrate is determined by sample rate and bit depth:
WAV/AIFF Bitrate Formula
CD Quality: 44,100 × 16 × 2 = 1,411,200 bps (1,411 kbps)
Choosing the Right Bitrate
The ideal bitrate depends on your content type and intended use:
Podcasts (Speech)
64-96 kbps monoVoice doesn't need high bitrates; saves bandwidth
Music Streaming
128-256 kbpsBalance of quality and bandwidth for streaming
Music Downloads
256-320 kbpsHigh quality for offline listening
Audiobooks
32-64 kbps monoLow bitrate is fine for narration
Archiving
FLAC/WAVUse lossless for master copies
Phone Calls/VoIP
8-32 kbpsHighly compressed for real-time transmission
How Bitrate Affects Splitting
Understanding bitrate helps when splitting audio files:
File Size Estimation
When splitting a file, you can estimate resulting segment sizes using the bitrate. A 60-minute 128 kbps file split into 10-minute segments will produce six ~9.4 MB files.
Quality Preservation
Proper lossless splitting preserves the original bitrate. Whether your source is 128 kbps or 320 kbps, the split segments maintain the same quality. Avoid tools that re-encode—they may change the bitrate and degrade quality.
VBR Splitting Considerations
VBR files don't have uniform data distribution. A 10-minute segment from the middle of a VBR file might be larger or smaller than a 10-minute segment from the end, depending on the audio complexity in each section.
Bitrate Myths Debunked
"Higher bitrate is always better"
Partially false. Above certain thresholds (256-320 kbps for MP3), most listeners can't hear improvement. Higher bitrates just waste storage space. For speech content, even 128 kbps is often excessive.
"Converting to higher bitrate improves quality"
False. Converting a 128 kbps MP3 to 320 kbps doesn't add quality—it just makes a bigger file with the same (or slightly worse) audio. You can't recover information that was already discarded.
"All 128 kbps files sound the same"
False. Encoding quality varies by encoder and settings. A 128 kbps AAC file typically sounds better than a 128 kbps MP3 from a poor encoder. Modern encoders produce better results than older ones at the same bitrate.
"VBR files can't be split properly"
False. VBR files can be split losslessly—the variable bitrate is preserved in each segment. Proper splitting tools handle VBR without issues.
Practical Bitrate Guide
| If You Need... | Use This Bitrate | Why |
|---|---|---|
| Smallest possible files | 64 kbps mono | Minimum acceptable for speech |
| Podcast distribution | 96 kbps mono / 128 kbps stereo | Standard podcast quality |
| Background music | 128-160 kbps | Good enough for casual listening |
| Active music listening | 192-256 kbps | High quality, reasonable size |
| Audiophile quality (lossy) | 320 kbps | Maximum MP3 quality |
| No compromise / archiving | FLAC / WAV | Lossless preserves everything |
Split Audio Files at Any Bitrate
ChunkAudio preserves your original bitrate and quality. Split high-fidelity FLAC or compact MP3 files—your choice, your quality.
Try ChunkAudio FreeFrequently Asked Questions
Audio bitrate measures how much data is used to encode each second of audio, expressed in kilobits per second (kbps). Higher bitrates mean more data and generally better quality. For example, 128 kbps MP3 uses 128,000 bits of data per second of audio.
CBR (Constant Bitrate) uses the same amount of data for every second of audio, making file sizes predictable. VBR (Variable Bitrate) uses more data for complex passages and less for simple ones, achieving better quality at similar file sizes. VBR is generally preferred for quality, CBR for streaming compatibility.
Proper lossless splitting preserves the original bitrate. The split files have the same quality and bitrate as the corresponding sections of the original file. Only re-encoding (which should be avoided for simple splits) would change the bitrate.
For speech-only podcasts, 64-96 kbps mono is sufficient and keeps file sizes small for downloads. If music is included, use 128 kbps stereo. Higher bitrates are unnecessary for voice content and just increase file sizes without audible improvement.
File size (MB) = (Bitrate in kbps × Duration in seconds) ÷ 8,000. For example, a 3-minute (180 second) MP3 at 128 kbps: (128 × 180) ÷ 8,000 = 2.88 MB. This formula gives approximate sizes; actual files may vary slightly due to headers and VBR encoding.
No. Converting a lower bitrate file to a higher bitrate doesn't improve quality—it just makes a larger file with the same audio. Once audio data is discarded during lossy compression, it can't be recovered. For better quality, you need to start with a higher quality source.