Audio Bitrate Converter

Audio Bitrate Converter – kbps, Mbps, File Size & PCM Calculator

Audio bitrate is the amount of data encoded per second in a digital audio stream, typically measured in kilobits per second (kbps). It is the single most important factor balancing audio quality against file size and bandwidth consumption. Whether you are encoding a podcast, mastering a music release, or configuring a streaming platform, understanding bitrate conversions and their downstream effects on file size is essential.

This converter handles four common workflows: converting a bitrate value between units (bps, kbps, Mbps, kBps, MBps), estimating the file size of an audio track from its bitrate and duration, calculating the bitrate required to reach a target file size, and computing the exact uncompressed PCM bitrate for WAV or AIFF audio from sample rate, bit depth, and channel count.

Bitrate Unit Conversion

All bit-based and byte-based data-rate units follow simple fixed ratios because 1 byte = 8 bits and each SI prefix represents a factor of 1,000:

• 1 kbps = 1,000 bps
• 1 Mbps = 1,000 kbps = 1,000,000 bps
• 1 kBps = 8 kbps
• 1 MBps = 8 Mbps

A common point of confusion is that internet service providers advertise speeds in Mbps (megabits) while operating systems report download progress in MB/s (megabytes). A 100 Mbps connection delivers roughly 12.5 MB/s — exactly one-eighth of the advertised megabit figure.

Estimating File Size from Bitrate and Duration

For constant bitrate (CBR) audio, the file size formula is straightforward:

File Size (bytes) = Bitrate (bps) × Duration (seconds) ÷ 8

For example, a 4-minute track (240 seconds) encoded at 192 kbps produces:

192,000 × 240 ÷ 8 = 5,760,000 bytes ≈ 5.49 MB

Note that most modern MP3 and AAC encoders use variable bitrate (VBR) by default, which allocates more bits to complex passages and fewer to silence. VBR files can be 10–20% smaller than CBR for the same perceived quality, so the calculated size is an upper-bound estimate for VBR files.

Calculating the Required Bitrate

If you need a track to fit within a specific file size — for example, a 5 MB limit for a newsletter attachment — the reverse formula gives you the maximum allowable bitrate:

Bitrate (kbps) = (File Size (bytes) × 8) ÷ Duration (seconds) ÷ 1,000

For a 3-minute 30-second (210-second) track with a 5 MB limit:

(5 × 1,048,576 × 8) ÷ 210 ÷ 1,000 ≈ 200 kbps

Uncompressed PCM / WAV Bitrate

Uncompressed audio formats like WAV and AIFF use PCM (Pulse-Code Modulation), where the bitrate is determined entirely by three parameters:

Bitrate (bps) = Sample Rate (Hz) × Bit Depth × Channels

CD-quality stereo audio uses 44,100 Hz, 16-bit, and 2 channels:

44,100 × 16 × 2 = 1,411,200 bps = 1,411.2 kbps ≈ 10.09 MB/min

Professional studio recording typically uses 48,000 Hz or 96,000 Hz at 24-bit with two channels, producing bitrates between 2.3 Mbps and 4.6 Mbps and files roughly 10× larger than compressed MP3 equivalents at the same duration.

Audio Quality Tiers by Bitrate

These conventions apply to modern lossy codecs (MP3, AAC) for stereo music content:

• Below 96 kbps (Low): Acceptable for voice, speech, or podcasts. Noticeable compression artifacts on music, especially in high-frequency content.
• 96–191 kbps (Medium): Suitable for general music streaming. Some listeners detect artifacts on critical material; common for radio streams and free-tier services.
• 192–319 kbps (High): Good quality suitable for most music listening. Spotify Premium and Apple Music use 256–320 kbps AAC.
• 320 kbps and above (Lossless-like): The maximum for standard MP3. At this bitrate most listeners cannot distinguish the compressed file from lossless audio in double-blind tests, though true lossless formats (FLAC, ALAC) remain preferred for archiving.

CBR vs VBR: Practical Guidance

CBR (Constant Bit Rate) encodes every frame at the same bitrate, making file size perfectly predictable. It is required for some broadcast workflows and low-latency streaming scenarios where decoders cannot buffer ahead.

VBR (Variable Bit Rate) dynamically adjusts the bitrate based on the complexity of each audio segment. A VBR encoder set to a quality target of "equivalent to 192 kbps" will use higher bitrates for dense musical passages and lower bitrates for quiet sections, resulting in smaller files with equal or better perceived quality compared to CBR at the same nominal bitrate.

For archiving, mastering, and distribution masters, always use lossless formats. For delivery and streaming, 256 kbps VBR AAC or 320 kbps MP3 CBR covers virtually all listening scenarios while remaining practical for storage and transfer.