Five minutes of 48 kHz, packed 24-bit stereo audio contain 86.4 MB of PCM data. At an average stream bitrate of 320 kbps, five minutes contain about 12 MB before tags and wrappers. Use the calculator to estimate a file, find recording time from available space, or count complete files that fit on a drive.
Choose PCM for uncompressed sample data, WAV or AIFF to add a wrapper allowance, or average bitrate for MP3, AAC and Opus. FLAC needs a range because its compression depends on the audio.
Audio file size calculator
Audio size & recording time
Enter settings only. This calculator does not open, upload or play audio.
Calculation details
- Batch total
- 86.40 MB
- Per minute
- 17.28 MB
- Data rate
- 2,304 kbps
- Classic RIFF boundary
- about 4 h 8 min
PCM payload is deterministic. A container and its metadata sit outside this byte count.
300 s × 48,000 samples/s × 24 bits × 2 channels ÷ 8 = 86,400,000 bytes.
PCM payload uses complete sample frames and the stored sample width. Fractional durations are rounded to the nearest frame. Here, 24-bit means packed three-byte samples; select 32 if your WAV stores each sample in four bytes. WAV and AIFF add an editable wrapper allowance. FLAC remains a planning band, not a guaranteed bound.
The audio file size formula
For uncompressed PCM, use bytes = seconds × sample rate × stored bits per sample × channels ÷ 8. A 60-second, 44.1 kHz, 16-bit stereo payload is 10,584,000 bytes: 10.584 MB or about 10.094 MiB. The selected width describes bytes stored, not just the converter’s useful precision.
The channel count multiplies complete sample frames. Mono has one sample per frame, stereo has two, and a six-channel recording has six. Microsoft’s current RIFF overview describes WAVE audio as chunks that include format information and the audio data itself. The PCM equation calculates the data; it doesn't account for every possible surrounding chunk.
Microsoft’s WAVEFORMATEXTENSIBLE definition distinguishes valid precision from stored sample width. For an existing PCM WAVE file, complete frame count multiplied by its block alignment gives the audio-data bytes without guessing that width. Other chunks still sit outside the payload.
For encoded audio, use estimated bytes = seconds × measured average bitrate in bits/s ÷ 8. A stream bitrate estimates encoded payload; an overall file bitrate calculated from complete file bytes and duration already includes metadata and container overhead. Do not add that overhead a second time. Sample rate and PCM depth alone do not determine an encoded file’s size.
Real-file checks behind the defaults
Our archived August 2026 check used FFmpeg 8.1.2: a 60-second, 48 kHz, 24-bit stereo silence file contained 17,280,000 PCM bytes. The saved WAV was 17,280,102 bytes and the AIFF was 17,280,054 bytes. Those measured overheads—102 and 54 bytes—are editable defaults, not format constants. Another writer can add metadata, padding, markers or broadcast chunks. The current FFmpeg download page lists 9.0.1 on September 12, 2026; the archived test is not a benchmark of that release.
| Test file | PCM or bitrate formula | Finished file | Observed difference |
|---|---|---|---|
| 60 s WAV, 48 kHz/24-bit stereo | 17,280,000 B | 17,280,102 B | +102 B |
| 60 s AIFF, 48 kHz/24-bit stereo | 17,280,000 B | 17,280,054 B | +54 B |
| 60 s MP3, CBR 128 kbps | 960,000 B | 960,515 B | +0.054% |
| 60 s MP3, CBR 320 kbps | 2,400,000 B | 2,401,220 B | +0.051% |
| 60 s AAC/M4A, target 256 kbps | 1,920,000 B | 1,665,647 B | −13.25% |
| 60 s FLAC pink noise, level 12 | 8,640,000 B PCM | 6,644,628 B | 76.91% of PCM |
The FFmpeg AAC test finished below its requested 256 kbps setting. That result belongs to that encoder and test signal, not to every AAC encoder. Apple’s AAC rate-control note separately explains CBR, ABR, constrained VBR and quality-based VBR. To plan a finished file, enter a measured average bitrate rather than treating a quality setting as a size guarantee.
Three calculations, three planning questions
Duration to file size
Use this before recording, rendering stems, or preparing delivery copies. Enter the longest file duration and the number of files. If a project mixes mono and stereo stems, calculate each group separately instead of pretending every file has the same channel count.
Storage to maximum recording time
Enter writable space, not advertised drive capacity. The three-copy figure divides an aggregate storage budget between one working source and two copies, allowing a wrapper for each copy. It does not measure three destinations. For independent backups, calculate each destination separately and use the shortest resulting recording time as the limit.
Drive capacity to whole files
Use this for repeated interviews, podcast episodes, or delivery batches. The result rounds down to complete files and also shows three-copy sets. A partial final file is not counted.
MB, MiB, GB, and GiB are different units
The BIPM SI prefix table defines mega as 10⁶ and giga as 10⁹. That makes 1 MB equal to 1,000,000 bytes and 1 GB equal to 1,000,000,000 bytes. The NIST binary-prefix reference defines 1 MiB as 2²⁰ bytes and 1 GiB as 2³⁰ bytes.
The same 1,048,576 bytes appear as 1.05 MB or 1.00 MiB after rounding. Neither display means data has disappeared. Compare raw bytes when checking a storage specification against a file browser; the calculator displays both unit systems.
WAV, AIFF, RF64, and BW64: payload is not the container
WAV and AIFF can carry uncompressed PCM, but they do not share one universal 44-byte wrapper. Each container has its own chunk structure, and real applications can write additional metadata. That is why the calculator has separate WAV and AIFF choices and exposes the wrapper allowance instead of silently adding 44 bytes to every PCM result.
The familiar “4 GB WAV limit” comes from classic RIFF’s 32-bit size fields. Plan around 4 GiB, or 4.29 decimal GB, with less available for audio after headers. The ITU-R BS.2088-2 recommendation defines BW64 for long-form audio. The EBU RF64 archive points to the ITU specification that superseded Tech 3306. For a long uninterrupted take, confirm that the recorder and receiving application both support the chosen large-file container; an extension alone is not proof of compatibility.
If the recording approaches that boundary, splitting at a safe edit point is often easier to exchange. The long-recording split guide covers the workflow. Do not lower sample rate or bit depth only to dodge a container limit without checking the delivery requirement. If conversion is required, review the sample-rate workflow and the bit-depth and dither guide before altering a master.
MP3, AAC, and Opus need an average-bitrate estimate
One hour at 128 kbps contains a nominal 57.6 MB of encoded payload. At 320 kbps it is 144 MB. Channel count should not be multiplied again when the selected bitrate already describes the complete stream, as it normally does in an export dialog.
CBR usually stays closest to the formula. ABR can miss the target, and a VBR quality setting may not expose a meaningful bitrate until after encoding. The safest workflow is to encode a representative passage, inspect its average, and use that measured value. The Sound Forge MP3 export guide explains the related export choices; the audio conversion guide covers format changes without overwriting the source.
Why FLAC must remain a range
FLAC reduces storage without discarding PCM information, but its result depends on the signal. Silence, steady tones, and correlated channels can compress strongly. Noise-like audio gives the predictor less redundancy to remove. Compression level changes encoder effort and can change size; it does not turn FLAC into a lossy codec.
The default 35–85% band is an editable planning assumption, not a measured confidence interval or a guaranteed minimum and maximum. Our archived 48 kHz/24-bit mono pink-noise test reached 80.01% of PCM at FFmpeg compression level 0 and 76.91% at level 12; silence reached 0.19%. These few synthetic files cannot predict your music library. Encode a representative passage and enter its measured percentage. The fields accept fractions below 1% and values above 100%, since short files or metadata can outweigh compression savings.
The current FLAC specification in RFC 9639 supports integer PCM with one to eight channels and bit depths from 4 to 32 bits; it does not directly preserve floating-point samples. The calculator disables larger FLAC choices, but a valid format ceiling does not guarantee that every player accepts every combination.
Plan the project footprint, not the delivery file
A 128 kbps MP3 can be the smallest object in the job. The source recording, edit master, rendered stems, alternate mixes, cache, and revisions usually dominate storage. Keep the preservation or edit master lossless, calculate delivery versions separately, and place independent backups on separate storage targets. For multichannel sessions, calculate the recorded channel count first; use the channel-conversion guide only when the delivery specification actually calls for a downmix.
The “three-copy sets” result is deliberately literal: one working source and two additional copies. It does not prove geographic separation, media health, or restoreability. Verify backups by opening or checksumming them, and test a restore before deleting cards or source drives.
Leave headroom on every destination. Filesystems, catalog databases, peak files, checksums, and application caches consume space outside the audio calculation. A recorder may also reserve space or stop before the advertised capacity is fully consumed. For field work, calculate with the card size you can actually write, then run a timed test at the exact channel count and recording format.
Five mistakes that break an audio storage estimate
- Calling every uncompressed result “WAV plus 44 bytes.” Calculate PCM first, then use the selected container’s actual or measured overhead.
- Using a target bitrate as if it were measured. ABR and VBR can finish above or below the setting.
- Multiplying total MP3 bitrate by channel count. The export bitrate usually describes the complete encoded stream.
- Treating FLAC as a fixed 50% saving. Measure representative material or retain a wide band.
- Budgeting one copy. Source, work files, delivery versions, revisions, and independent backups all consume space.
For a deadline-critical recording, make a short test with the actual recorder, codec, metadata and destination filesystem. Compare its bytes and duration with this estimate before recording the full session. For other measurements, use the audio tools hub; this calculator plans storage and does not inspect audio.
Audio file size calculator FAQ
How do I calculate an audio file size?
For PCM, multiply seconds by sample rate, stored bits per sample and channels, then divide by eight. The 24-bit choice assumes packed three-byte samples; choose 32 if each sample occupies four bytes. For encoded audio, multiply seconds by the measured average bitrate in bits per second and divide by eight. An overall file bitrate already includes wrapper overhead.
How many MB is one minute of audio?
At 44.1 kHz/16-bit stereo, one minute contains 10.584 MB of PCM payload. At 48 kHz/24-bit stereo it contains 17.28 MB. A one-minute 128 kbps stream contains about 0.96 MB before tags and container overhead.
How many GB is a three-hour audio file?
It depends on the format. Three hours of 48 kHz/24-bit stereo PCM contain 3.1104 GB. At 128 kbps, the encoded payload is about 172.8 MB; at 320 kbps it is about 432 MB.
How many GB is one hour of MP3?
At a measured average of 128 kbps, one hour is about 57.6 MB or 0.0576 GB before tags and container overhead. At 320 kbps, it is about 144 MB or 0.144 GB.
Why is my WAV larger than the PCM calculation?
WAV may store each sample in more bits than its valid precision, such as 24 valid bits in a 32-bit container. It also adds RIFF chunks, metadata and padding. First match the stored sample width, then add measured wrapper overhead; do not treat sample padding as a fixed header.
Can I calculate FLAC size exactly before encoding?
No. FLAC size depends on the signal and encoder settings. Use a planning range, then encode a representative minute and measure its ratio to the PCM source.
Why do Finder and another tool show different file sizes?
They may be using decimal MB and GB versus binary MiB and GiB, or they may round differently. Compare the raw byte count before assuming either tool is wrong.
What happens when a WAV reaches the classic 4 GB boundary?
Classic RIFF/WAV has 32-bit size fields. Use a workflow that supports RF64 or BW64, or split the recording before the boundary, and verify compatibility at both ends.