How to calculate audio file size
Audio file size depends on how much data is stored for every second of audio and how long the recording lasts.
Uncompressed PCM audio uses the sample rate, bit depth and channel count directly. Compressed audio is more conveniently estimated from its average bitrate.
PCM and WAV file size formula
For uncompressed PCM audio, first calculate the number of bytes stored each second.
The division by 8 converts bits to bytes.
PCM example: 48 kHz, 24-bit stereo
A 48 kHz, 24-bit stereo recording stores:
For five minutes, or 300 seconds:
That is approximately 86.4 MB using decimal megabytes, or about 82.4 MiB using binary mebibytes.
Compressed audio file size
MP3, AAC, Opus and other compressed formats are commonly described by bitrate in kilobits per second.
For example, five minutes of audio at 320 kbps is approximately 12 MB before small format, metadata and container overhead.
Constant vs. variable bitrate
Constant bitrate audio uses a predictable data rate, so its size can be estimated directly from bitrate and duration.
Variable bitrate audio changes its bitrate as the content changes. For VBR files, use the expected or measured average bitrate. The result is then an estimate rather than an exact file size.
Calculate recording time from storage
The calculator also works in reverse. Select Duration from storage, enter the available storage, and choose the recording settings.
This is useful when planning field recordings, podcasts, interviews, studio sessions or long-form audio capture.
Sample rate
Sample rate is the number of audio samples stored each second. Common values include 44.1 kHz for music and 48 kHz for many video and professional audio workflows.
Higher sample rates store more samples each second and therefore increase uncompressed file size when bit depth, channels and duration remain unchanged.
Bit depth
Bit depth determines how many bits are used to store each PCM sample. Common uncompressed formats include 16-bit and 24-bit audio.
Moving from 16-bit to 24-bit increases the uncompressed sample data by 50% when every other setting stays the same.
Mono, stereo and multichannel audio
Channel count affects PCM size directly. Stereo stores two channels, so it requires twice the PCM sample data of mono at the same sample rate, bit depth and duration.
Multichannel recordings require still more storage because each channel contributes its own stream of PCM samples.
MB vs. MiB
A decimal megabyte (MB) contains 1,000,000 bytes. A binary mebibyte (MiB) contains 1,048,576 bytes.
This calculator shows both so the apparent difference between storage figures is clear rather than treating the units as interchangeable.
GB vs. GiB
The same distinction applies to larger storage units. One decimal gigabyte contains one billion bytes, while one gibibyte contains 1,073,741,824 bytes.
WAV header and metadata
The PCM calculation represents the audio sample payload. WAV files also contain a header and can contain metadata or additional chunks.
For ordinary recordings this overhead is usually very small compared with the PCM sample data, but the exact file size can differ slightly from the calculated value.
Compressed format overhead
Compressed audio files can contain metadata, tags, container structures, headers and other information in addition to encoded audio.
The bitrate calculation is therefore best treated as an audio-data estimate rather than a guarantee of the exact final byte count.
Audio file size vs. video file size
Video storage usually combines a much larger video stream with one or more audio streams.
For video bitrate and duration calculations, use the Video File Size Calculator.
Related digital calculators
For general conversions between file-size units, use the File Size Calculator.
To estimate how long a file takes to download, use the Download Time Calculator.
To calculate transfer duration from a file size and data rate, use the Data Transfer Calculator.
PCM calculations estimate the uncompressed sample payload. Compressed calculations use the selected average bitrate. Headers, metadata, VBR behavior, codec framing and application-specific overhead can make the actual stored file slightly larger or smaller.
Frequently asked questions
How large is one minute of 48 kHz 24-bit stereo WAV?
The PCM sample data is about 17.28 MB per minute, or roughly 16.48 MiB.
How large is five minutes of 320 kbps audio?
The encoded audio data is approximately 12 MB before small metadata and format overhead.
Does stereo use twice the space of mono?
For uncompressed PCM using the same sample rate, bit depth and duration, stereo uses twice the sample data because it stores two channels instead of one.
Can I calculate recording time from an SD card or drive size?
Yes. Switch the calculator to duration-from-storage mode and enter the usable storage amount and audio settings.
Is VBR audio size exact?
No. Variable bitrate changes through the recording, so the result depends on the average bitrate actually produced by the encoder.
Using this calculator effectively
The Audio File Size Calculator estimates storage for uncompressed PCM or WAV audio from sample rate, bit depth, channels and duration, or for compressed audio from average bitrate and duration. It can also work in reverse to estimate recording time from available storage.
Common uses
- Planning storage for WAV, PCM, podcast, interview, music or field-recording sessions.
- Estimating MP3, AAC, Opus or other compressed audio size from average bitrate and duration.
- Checking how much recording time fits on a memory card, recorder, computer or external drive.
Tips for a better estimate
- Use the actual sample rate, bit depth and channel count for uncompressed PCM recordings.
- For variable-bitrate compressed audio, use the expected average bitrate rather than the peak bitrate.
- Allow additional space for headers, metadata, container structures and application-specific overhead.
Related calculations
Video File Size Calculator · Download Time Calculator · File Size Calculator