How Big Is an Audio File? Size by Bitrate, Format, and Duration

Audio file size can range from less than one megabyte for a short compressed voice recording to several gigabytes for a long, uncompressed multichannel production.

The size depends primarily on the duration and the amount of data used per second. For compressed formats such as MP3 and AAC, this amount is usually represented by bitrate. For uncompressed PCM audio such as WAV, file size is determined by sample rate, bit depth, channel count, and duration.

A 60-minute podcast encoded at 128 Kbps uses approximately 57.6 MB. The same hour stored as 48 kHz, 24-bit stereo PCM requires approximately 1.04 GB before minor file overhead.

That difference is why creators often use one format for recording and editing and another format for publishing.

Use the Audio File Size Calculator to estimate storage from bitrate and duration.

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Quick Audio File Size Estimates

The following table shows approximate file sizes for constant-bitrate compressed audio. It uses decimal storage units and does not include small amounts of metadata or container overhead.

These values are suitable for planning MP3, AAC, and other compressed files when the average bitrate is known.

Variable-bitrate encoding may produce a smaller or larger file depending on the complexity of the audio.

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What Determines Audio File Size?

Audio file size is determined by how much data is stored and how long the recording lasts.

The relevant settings depend on whether the file is compressed or uncompressed.

Compressed Audio

For compressed audio, the main factors are:

• Bitrate
• Duration
• Constant or variable bitrate
• Codec
• Channel configuration
• Metadata and embedded artwork

Common compressed formats include:

• MP3
• AAC
• Opus
• Ogg Vorbis
• WMA

Uncompressed Audio

For uncompressed PCM audio, the main factors are:

• Sample rate
• Bit depth
• Number of channels
• Duration

WAV is a common container for uncompressed PCM audio, although a WAV file can technically contain other types of encoded audio.

Lossless Compressed Audio

Lossless formats preserve the original audio data while reducing file size.

Common examples include:

• FLAC
• ALAC

Their final sizes depend on how efficiently the source audio can be compressed. Silence and simple material may compress more effectively than dense or noisy recordings.

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How to Calculate Compressed Audio File Size

For compressed audio with a known bitrate, use:

File size = bitrate × duration ÷ 8

The division by eight converts bits into bytes.

When bitrate is measured in Kbps and duration is measured in seconds:

File size in MB = bitrate in Kbps × duration in seconds ÷ 8 ÷ 1,000

For a quick per-minute calculation:

MB per minute = bitrate in Kbps × 0.0075

Example: 128 Kbps for 60 Minutes

Convert the duration:

60 minutes = 3,600 seconds

Calculate the number of kilobits:

128 × 3,600 = 460,800 kilobits

Convert to megabytes:

460,800 ÷ 8 ÷ 1,000 = 57.6 MB

A 60-minute file at 128 Kbps is approximately 57.6 MB.

Example: 320 Kbps for 10 Minutes

320 × 600 ÷ 8 ÷ 1,000 = 24 MB

A 10-minute file at 320 Kbps is approximately 24 MB.

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How Much Space Does MP3 Audio Use?

MP3 is a lossy compressed format. It reduces file size by removing and simplifying audio information according to its encoding model and bitrate.

Common MP3 bitrates include:

• 32 Kbps
• 64 Kbps
• 96 Kbps
• 128 Kbps
• 160 Kbps
• 192 Kbps
• 256 Kbps
• 320 Kbps

MP3 File Size per Hour

A mono voice recording may not require the same bitrate as stereo music. The appropriate setting depends on the content, codec, distribution platform, and acceptable quality.

Repeatedly converting an MP3 into another lossy format can reduce quality. If possible, create new delivery files from an uncompressed or lossless master.

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How Much Space Does AAC Audio Use?

AAC is another lossy audio codec commonly used in video files, streaming services, podcasts, and mobile workflows.

At the same nominal bitrate and duration, AAC and MP3 files are approximately the same size.

For example:

• One hour at 128 Kbps: approximately 57.6 MB
• One hour at 192 Kbps: approximately 86.4 MB
• One hour at 256 Kbps: approximately 115.2 MB
• One hour at 320 Kbps: approximately 144 MB

The codec may produce different perceived quality at the same bitrate, but the size calculation remains based on the bitrate and duration.

Apple Podcasts states that, at the same bitrate, AAC can provide better audio quality than MP3. It accepts MP3 or AAC audio for RSS-delivered podcast episodes.

AAC-LC is also commonly recommended for audio included with online video.

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How Much Space Does WAV Audio Use?

WAV is a container rather than a single compression method. In many recording and editing workflows, a WAV file contains uncompressed PCM audio.

For uncompressed PCM, use:

Bitrate = sample rate × bit depth × channels

Then:

File size = bitrate × duration ÷ 8

44.1 kHz, 16-Bit Mono

44,100 × 16 × 1 = 705,600 bits per second

This equals approximately:

• 88,200 bytes per second
• 5.29 MB per minute
• 317.52 MB per hour

44.1 kHz, 16-Bit Stereo

Stereo contains two channels:

44,100 × 16 × 2 = 1,411,200 bits per second

This equals approximately:

• 176,400 bytes per second
• 10.58 MB per minute
• 635.04 MB per hour

48 kHz, 24-Bit Stereo

48,000 × 24 × 2 = 2,304,000 bits per second

This equals approximately:

• 288,000 bytes per second
• 17.28 MB per minute
• 1.04 GB per hour

WAV files can therefore be many times larger than compressed MP3 or AAC delivery files.

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Uncompressed Audio Storage Table

The following estimates use uncompressed PCM audio and decimal storage units.

Headers, metadata, broadcast information, markers, and other chunks can make the actual WAV file slightly larger.

Professional multitrack sessions require far more storage because each microphone or instrument may be recorded as a separate uncompressed channel.

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How Much Space Does FLAC Audio Use?

FLAC uses lossless compression. When decoded, it restores the original audio data without the information loss associated with MP3 or AAC.

Unlike uncompressed PCM, FLAC does not have one fixed file size for a given sample rate and bit depth. Its compression performance depends on the source.

Factors include:

• Silence
• Repetition
• Background noise
• Music complexity
• Number of channels
• Sample rate
• Bit depth
• Encoder settings
• Embedded artwork and metadata

A FLAC file is normally smaller than its uncompressed PCM source but larger than a heavily compressed MP3 or AAC file.

Because the compression ratio varies, the most reliable method is to encode a representative sample or inspect the average bitrate of an existing file.

Do not assume that every FLAC file will be a fixed percentage of the WAV version.

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MP3 vs. AAC vs. WAV vs. FLAC

No single format is best for every stage.

A common workflow is:

1. Record and edit in WAV or another high-quality production format.
2. Keep a lossless master.
3. Export MP3 or AAC for distribution.
4. Preserve project files and source recordings separately.

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What Is Audio Bitrate?

Audio bitrate is the amount of data used for each second of audio.

It is commonly measured in Kbps, or kilobits per second.

A 128 Kbps file uses approximately 128,000 bits every second. A 320 Kbps file uses approximately 320,000 bits every second.

If the duration remains unchanged:

• Doubling the bitrate approximately doubles the file size
• Halving the bitrate approximately halves the file size

For example, one hour of audio uses approximately:

• 57.6 MB at 128 Kbps
• 115.2 MB at 256 Kbps
• 144 MB at 320 Kbps

A higher bitrate provides the codec with more data, but it does not automatically repair poor recording quality, clipping, background noise, microphone problems, or previous compression damage.

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CBR vs. VBR Audio File Size

Compressed audio can use constant or variable bitrate encoding.

Constant Bitrate

CBR uses a relatively consistent bitrate throughout the file.

A 128 Kbps CBR recording is straightforward to estimate because each second uses approximately the same amount of data.

CBR is useful when:

• Predictable file size matters
• A platform requires it
• Streaming behavior must remain consistent
• Compatibility is a concern

Variable Bitrate

VBR changes the bitrate according to the audio content.

Simple passages may use less data, while complex passages may use more. VBR can improve encoding efficiency because it does not allocate the same amount of data to silence and dense music.

The final size depends on the actual average bitrate rather than only the maximum bitrate.

If a VBR file averages 146 Kbps for one hour:

146 × 3,600 ÷ 8 ÷ 1,000 = 65.7 MB

A bitrate shown as the maximum setting should not be used as the average unless the encoder documentation confirms that behavior.

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Sample Rate and Audio File Size

Sample rate describes how many samples of the audio waveform are stored each second.

Common sample rates include:

• 22.05 kHz
• 24 kHz
• 44.1 kHz
• 48 kHz
• 88.2 kHz
• 96 kHz
• 176.4 kHz
• 192 kHz

A sample rate of 48 kHz records 48,000 samples per second for each channel.

For uncompressed audio, increasing the sample rate directly increases file size.

For example, 24-bit stereo PCM uses approximately:

• 1.04 GB per hour at 48 kHz
• 2.07 GB per hour at 96 kHz
• 4.15 GB per hour at 192 kHz

Doubling the sample rate doubles the raw data rate when bit depth and channel count remain unchanged.

For compressed MP3 or AAC files with a fixed bitrate, sample rate does not directly change the calculated file size because the bitrate already defines the amount of data per second. It can still affect encoder behavior, compatibility, and quality.

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Bit Depth and Audio File Size

Bit depth describes how many bits are available for each sample.

Common bit depths include:

• 16-bit
• 24-bit
• 32-bit integer
• 32-bit floating point

For uncompressed PCM audio, increasing bit depth increases file size proportionally.

At the same sample rate and channel count:

• 24-bit audio uses 50% more sample data than 16-bit audio
• 32-bit audio uses twice the sample data of 16-bit audio

Bit depth is also related to the representable dynamic range and processing headroom, depending on the audio format and workflow.

Higher bit depth is useful during recording and editing, but it should not be selected solely because a larger number appears better. The recording equipment, noise floor, software, distribution requirements, and production process all matter.

Converting a 16-bit source to 24-bit does not restore detail that was not captured in the original file.

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Mono, Stereo, and Multichannel Audio

Channel count has a direct effect on uncompressed file size.

At identical sample rate, bit depth, and duration:

• Stereo uses twice as much raw data as mono
• Six-channel audio uses six times as much raw data as mono
• Eight-channel audio uses eight times as much raw data as mono

Example: 48 kHz, 24-Bit PCM

The approximate storage per hour is:

Compressed formats may allocate bitrate differently across channels, so file size should be calculated from the total encoded bitrate when that value is available.

A voice-only podcast recorded with one microphone may be distributed in mono. Music, environmental recordings, and productions using spatial information may require stereo or multichannel audio.

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Podcast File Size by Duration

Apple Podcasts accepts MP3 or AAC for RSS feed audio. Its current recommendations include bitrate ranges based on sample rate and channel count.

For audio at 44.1 or 48 kHz, Apple lists:

• Mono: 64–128 Kbps
• Stereo: 128–256 Kbps

The following table provides approximate podcast sizes.

These estimates exclude embedded artwork and metadata.

Large cover images can noticeably increase the size of short, low-bitrate podcast files. Optimize artwork separately rather than reducing the audio quality to compensate for oversized images.

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Audio File Size Inside a Video

A video file normally contains both video and audio streams.

The combined bitrate is approximately:

Total bitrate = video bitrate + audio bitrate

Suppose a video uses:

• Video bitrate: 8 Mbps
• Audio bitrate: 384 Kbps
• Duration: 60 minutes

Convert the audio bitrate:

384 Kbps = 0.384 Mbps

Add the two:

8 + 0.384 = 8.384 Mbps

Calculate the size:

8.384 × 3,600 ÷ 8 = 3,772.8 MB

The combined video and audio streams use approximately 3.77 GB before minor container overhead.

In this example, the audio accounts for approximately 172.8 MB.

For more complete video storage calculations, read How Much Storage Does Video Use? File Size by Resolution and Duration.

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How Many Hours of Audio Fit on a Storage Drive?

The following table estimates compressed audio capacity using decimal storage units.

The actual usable capacity will be lower because of formatting, other files, application data, artwork, metadata, and the difference between decimal and binary storage units.

Production projects also need space for source recordings, alternate takes, session files, backups, and exports.

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Planning Storage for Multitrack Audio

The finished mix is often much smaller than the full production session.

Suppose a podcast records four separate microphones for two hours at 48 kHz, 24-bit mono PCM.

One channel uses approximately 518.4 MB per hour.

Calculate the source storage:

518.4 MB × 4 channels × 2 hours = 4,147.2 MB

The original recordings require approximately 4.15 GB.

The project may also include:

• Music
• Sound effects
• Room recordings
• Alternate takes
• Processed copies
• Automatic backups
• Rendered previews
• Session files
• Final WAV masters
• MP3 or AAC distribution files

A two-hour published podcast may be under 250 MB, while its working project requires several gigabytes.

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Decimal MB vs. Binary MiB

Storage tools may display different values because decimal and binary units are both used.

Decimal units use:

• 1 KB = 1,000 bytes
• 1 MB = 1,000,000 bytes
• 1 GB = 1,000,000,000 bytes

Binary units use:

• 1 KiB = 1,024 bytes
• 1 MiB = 1,048,576 bytes
• 1 GiB = 1,073,741,824 bytes

A file described as 100 MB in decimal units is approximately 95.37 MiB.

This difference does not indicate missing data. The same number of bytes is being represented with different units.

Check which convention is used when a platform imposes a strict file-size limit.

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Why the Actual File Size May Differ

A calculated value is an estimate. The actual result may differ because of:

• Variable bitrate encoding
• File headers
• Container overhead
• Metadata
• Embedded artwork
• Chapter information
• Multiple audio tracks
• Encoder padding
• Error correction
• Codec implementation
• Rounding
• Silence handling

A constant-bitrate file usually stays close to the calculated value, while a variable-bitrate or lossless file may vary more significantly.

For strict limits, create a shorter test export or leave a safety margin below the maximum permitted size.

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How to Reduce Audio File Size

Lower the Bitrate

Reducing bitrate directly lowers the size of MP3, AAC, and other compressed files.

Listen carefully for:

• Swirling artifacts
• Harsh consonants
• Metallic sound
• Reduced stereo detail
• Weak transients
• Distorted background music
• Unnatural ambience

Use Mono for Appropriate Voice Content

A single-speaker voice recording may not require stereo delivery. Encoding suitable content as mono can reduce the amount of data required.

Do not convert music or spatial recordings to mono without checking the artistic and technical consequences.

Use an Efficient Codec

AAC or Opus may provide useful efficiency for supported workflows. Compatibility must be confirmed before replacing a widely supported format such as MP3.

Trim Silence and Unused Material

Duration directly affects file size. Remove unnecessary silence, false starts, unused introductions, and trailing audio.

Optimize Embedded Artwork

A large image embedded in every audio file can add unnecessary storage. Resize and compress artwork according to the destination’s requirements.

Export from the Master

Create a new compressed file from a lossless master instead of repeatedly re-encoding an MP3 or AAC file.

Repeated lossy conversion can reduce quality even if the final bitrate is high.

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Choosing Audio Settings by Use Case

Spoken-Word Podcast

A practical starting range is:

• Format: AAC or MP3
• Sample rate: 44.1 or 48 kHz
• Channels: Mono when stereo is unnecessary
• Bitrate: Within the distribution platform’s recommended range

Apple currently lists 64–128 Kbps for mono RSS audio at 44.1 or 48 kHz.

Stereo Podcast with Music

A practical starting range is:

• Format: AAC or MP3
• Sample rate: 44.1 or 48 kHz
• Channels: Stereo
• Bitrate: 128–256 Kbps

Music, ambience, and stereo effects may benefit from more data than a simple mono voice recording.

Audio for Online Video

For video platforms:

• Format: AAC-LC is commonly supported
• Sample rate: 48 kHz is widely used for video
• Channels: Stereo unless the project requires another configuration
• Bitrate: Follow the destination platform’s current recommendation

Vimeo recommends AAC-LC, 48 kHz, and provides 320 Kbps CBR as a consistent high-quality setting, while noting that the appropriate data rate depends on the audio configuration.

Recording and Editing

For production:

• Format: WAV or another suitable lossless format
• Sample rate: Match the project
• Bit depth: Commonly 24-bit for recording
• Channels: Record sources separately when appropriate

The production master will be much larger than the delivery copy.

Archival Storage

For archiving:

• Preserve the original recording
• Keep a lossless master
• Store project files and documentation
• Verify backups
• Avoid using a lossy file as the only master

FLAC or another lossless format may reduce storage while preserving the original audio data, depending on workflow compatibility.

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Common Audio File Size Mistakes

Confusing Kbps and KB/s

Kbps means kilobits per second. KB/s means kilobytes per second.

Because eight bits equal one byte:

128 Kbps = approximately 16 KB/s

Ignoring Channel Count

Stereo uncompressed audio requires twice the raw storage of mono at the same sample rate and bit depth.

Treating WAV as One Fixed Quality

WAV is a container. Its size depends on the audio encoding and settings inside it.

Assuming FLAC Has a Fixed Bitrate

FLAC is lossless and normally uses a variable data rate. Its size depends on the source material and encoding settings.

Increasing Bitrate After Compression

Converting a 64 Kbps MP3 into a 320 Kbps MP3 makes the new file larger but does not restore information removed by the first encode.

Using Distribution Files as Masters

MP3 and AAC files are useful for delivery but should not replace lossless production masters when future editing is expected.

Forgetting Embedded Artwork

Large artwork can significantly increase small podcast or music files.

Calculating Only the Final Mix

Multitrack source recordings can require many times more storage than the published file.

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Frequently Asked Questions

How large is one hour of audio at 128 Kbps?

Approximately 57.6 MB, excluding metadata and minor overhead.

How large is one hour of audio at 320 Kbps?

Approximately 144 MB.

How large is one hour of WAV audio?

It depends on sample rate, bit depth, and channels. One hour of 44.1 kHz, 16-bit stereo PCM is approximately 635 MB. One hour of 48 kHz, 24-bit stereo PCM is approximately 1.04 GB.

Is AAC smaller than MP3?

At the same bitrate and duration, the files are approximately the same size. AAC may provide better perceived quality at the same bitrate in supported workflows.

Is FLAC smaller than WAV?

A FLAC file is normally smaller than the equivalent uncompressed PCM source, but the exact compression ratio varies with the audio.

Does sample rate affect MP3 size?

For a fixed-bitrate MP3, the bitrate and duration determine the approximate size. Sample rate can affect encoding quality and compatibility but does not change the fixed amount of data per second.

Does bit depth affect WAV size?

Yes. For uncompressed PCM, increasing bit depth increases the data stored for every sample.

Does stereo double file size?

For uncompressed PCM, stereo uses twice the data of mono. For compressed audio, use the total encoded bitrate to calculate the size.

How large is a two-hour podcast?

At 128 Kbps, approximately 115.2 MB. At 192 Kbps, approximately 172.8 MB. At 256 Kbps, approximately 230.4 MB.

Can I calculate audio size from duration alone?

Not accurately. You also need the compressed bitrate or, for uncompressed audio, the sample rate, bit depth, and channel count.

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Final Recommendations

For compressed audio, estimate file size with:

File size = bitrate × duration ÷ 8

For uncompressed PCM, use:

File size = sample rate × bit depth × channels × duration ÷ 8

When planning a project:

1. Identify whether the file is compressed, lossless, or uncompressed.
2. Use the average bitrate for MP3, AAC, Opus, and similar formats.
3. Use sample rate, bit depth, and channels for PCM audio.
4. Include every track in a multitrack recording.
5. Allow space for masters, edits, exports, and backups.
6. Leave a safety margin for metadata and overhead.
7. Confirm the destination platform’s current specifications.
8. Preserve a lossless master when future editing is likely.

Use the Audio File Size Calculator for compressed audio estimates based on bitrate and duration.

Audio distribution files are often small, but production storage can grow quickly. The best estimate is based on the actual recording or export settings rather than the filename extension alone.