Enter a recording length and a bitrate (MP3, AAC) or sample rate, bit depth, and channels (WAV, AIFF) to see the file size, MB per minute, and how long you can record within a size limit.
Audio format
Recording length
Estimated file size
Per minute
960 KB
Per hour
57.6 MB
Formula
128 kbps × 1,000 ÷ 8 × 1,800 sec = ~28.8 MB
Size units
File size at each bitrate
Recording time that fits on a drive
USB flash drive (16 GB)
~277 hr 46 min 40 sec
Phone free space (64 GB)
~1111 hr 6 min 40 sec
SD card (128 GB)
~2222 hr 13 min 20 sec
External hard drive (1,000 GB)
~17361 hr 6 min 40 sec
TIP
128 kbps or lower is a common choice for speech. For music or recordings with background audio, 192 kbps or higher keeps more detail.
Bitrate
Longest recording for a size limit
Email attachments are encoded before sending and end up larger than the file on disk, so stay comfortably under the limit. Platform limits can change.
Maximum length at current settings
~26 min 2 sec
How Audio File Size Is Calculated
A recording's size is its data rate multiplied by its length. Thirty minutes at 128 kbps comes to about 28.8 MB. The same thirty minutes saved as CD-quality WAV is about 317 MB.
The calculator covers two cases. For compressed formats such as MP3, AAC, and Opus, you pick a bitrate in kbps. For uncompressed audio such as WAV and AIFF, you pick the sample rate, bit depth, and number of channels. It also shows size per minute and per hour, compares common bitrates for your recording length, estimates how much recording time fits on a drive, and works backward from a size limit.
Use it before you record or export to check an email attachment limit, a podcast host's upload cap, or the free space on a recorder or phone.
Typical Uses: Podcasts, Voice Memos, and Storage Planning
Planning a podcast or interview
Enter the planned length and your export bitrate to see the file size before you record, then compare it with your host's upload limit.
Sending a voice memo by email or chat
Type a size limit such as 25 MB and see the longest recording that fits at the current settings.
Checking recorder or phone storage
See how many hours fit on an SD card, USB drive, or phone at your bitrate or PCM settings.
Choosing between WAV and MP3
Compare the size of the same recording at different settings and weigh sound quality against disk space.
How to Estimate a Recording's Size in 4 Steps
- Choose Compressed (MP3, AAC, Opus) or Uncompressed (WAV, AIFF).
- Enter the recording length in hours, minutes, and seconds, or tap a preset.
- For compressed audio, pick a bitrate in kbps. For uncompressed audio, pick the sample rate, bit depth, and channels.
- Read the estimated size, the MB per minute, and the bitrate and storage comparisons. They update as you change settings.
Note: The calculation runs in your browser, and your settings are not sent to a server.
Accuracy Limits and Assumptions
- Estimates assume a constant bitrate. Variable bitrate (VBR) files can come out smaller or larger, and tags and container headers add a small amount.
- In compressed mode the bitrate is the total for the whole stream, so mono and stereo give the same estimate at the same bitrate.
- Uncompressed mode gives the raw PCM size. FLAC and ALAC files hold the same audio in less space, so treat the result as an upper estimate for them.
- MB and GB use 1,000-based units by default (1 MB = 1,000,000 bytes). Switch to 1,024-based units if you want to match a program that counts 1 MB as 1,048,576 bytes.
- For a final check, compare the estimate with the properties of a file you have actually exported.
MP3 and AAC Size Chart: MB by Length and Bitrate
Estimated size for common recording lengths at four popular bitrates, using 1 MB = 1,000,000 bytes.
| Length | 128 kbps | 192 kbps | 256 kbps | 320 kbps |
|---|---|---|---|---|
| 3 min (one song) | 2.9 MB | 4.3 MB | 5.8 MB | 7.2 MB |
| 10 min (voice memo) | 9.6 MB | 14.4 MB | 19.2 MB | 24.0 MB |
| 30 min (meeting) | 28.8 MB | 43.2 MB | 57.6 MB | 72.0 MB |
| 1 hr (lecture) | 57.6 MB | 86.4 MB | 115.2 MB | 144.0 MB |
| 3 hr (radio show) | 172.8 MB | 259.2 MB | 345.6 MB | 432.0 MB |
| 10 hr (audiobook) | 576.0 MB | 864.0 MB | 1.15 GB | 1.44 GB |
Values assume a constant bitrate with no tag or header overhead. For other settings, use the calculator above.
Bitrate, Sample Rate, and Format: What Drives Size
The numbers behind the estimate, and how to pick settings for your recording.
The formula: data rate × duration
For compressed audio, size in bytes = bitrate (kbps) × 1,000 ÷ 8 × seconds. For uncompressed audio, size in bytes = sample rate × bit depth × channels ÷ 8 × seconds.
Example: 128 kbps for 60 seconds is 128 × 1,000 ÷ 8 × 60 = 960,000 bytes, or about 0.96 MB.
Kilobits versus kilobytes
Bitrate is measured in bits, and file sizes in bytes. Divide by 8 to convert: 128 kbps equals 16 kilobytes per second.
Megabytes can also mean two things. Some programs count 1 MB as 1,000,000 bytes and others as 1,048,576 bytes. The tool lets you pick either.
Choosing a bitrate
For speech, 64 to 128 kbps is commonly used. For music, 192 to 320 kbps is typical, and 320 kbps is the highest standard MP3 bitrate.
Size grows in direct proportion to bitrate, so 256 kbps makes a file twice as large as 128 kbps for the same length.
Why WAV files are so much larger
WAV stores every sample. CD quality (44.1 kHz, 16-bit, stereo) is 44,100 × 16 × 2 ÷ 8 = 176,400 bytes per second, about 10.6 MB per minute. A 192 kbps MP3 is about 1.44 MB per minute, roughly one seventh of that.
Other common settings: 48 kHz / 16-bit stereo is about 11.5 MB per minute, 48 kHz / 24-bit stereo about 17.3 MB, and 96 kHz / 24-bit stereo about 34.6 MB. FLAC stores the same audio losslessly in a smaller file.
Fitting an upload or email limit
Divide the limit by the data rate to get the maximum length. At 128 kbps, which is 16,000 bytes per second, a 25 MB limit allows about 26 minutes.
Email attachments are encoded for sending and grow in transit, so aim well below the stated limit. The size-limit section of the calculator does this division for you.
Common Mistakes When Planning Recording Size
Planning by length alone
A recording's length says little about its size until you know the bitrate. One hour is about 29 MB at 64 kbps and about 635 MB as CD-quality WAV.
💡 See the solution▼
Mixing up kilobits and kilobytes
A bitrate of 128 kbps is 128 kilobits per second, which is 16 kilobytes per second. Reading it as 128 KB per second overstates the size by eight times.
💡 See the solution▼
Cutting it close to an email limit
A file just under 25 MB can still be rejected, because attachments are encoded for sending and become larger than the file on disk.
💡 See the solution▼
Running out of space mid-recording
A long session can fill a recorder or phone and stop partway through if you did not check the free space against your settings.
💡 See the solution▼
Recording a long session as WAV without checking the size
Uncompressed audio at 24-bit and a high sample rate can reach several gigabytes in a single session, which is hard to store and share.
💡 See the solution▼
Questions About Bitrate, WAV, and MP3 Size
Q.How do you calculate audio file size?
A. For compressed formats such as MP3 and AAC, size in bytes = bitrate in kbps × 1,000 ÷ 8 × length in seconds. For uncompressed formats such as WAV, size in bytes = sample rate × bit depth × channels ÷ 8 × length in seconds. This calculator applies the formula for you.
Q.How many MB is one minute of audio?
A. An MP3 or AAC file at 128 kbps is about 0.96 MB per minute, 192 kbps is about 1.44 MB, 256 kbps is about 1.92 MB, and 320 kbps is about 2.4 MB. CD-quality WAV (44.1 kHz, 16-bit, stereo) is about 10.6 MB per minute. These figures use 1 MB = 1,000,000 bytes.
Q.What bitrate should I use?
A. For speech, 64 to 128 kbps is commonly used. For music, 192 to 320 kbps is typical, and 320 kbps is the highest standard MP3 bitrate. File size scales directly with bitrate, so doubling the bitrate doubles the file.
Q.How much bigger is a WAV file than an MP3?
A. CD-quality WAV runs at 176,400 bytes per second. A 128 kbps MP3 uses 16,000 bytes per second, so the WAV is about 11 times larger. Against a 192 kbps MP3 (24,000 bytes per second) it is about 7 times larger.
Q.How long can I record and stay under 25 MB?
A. Use the size-limit section: enter 25 and the tool shows the longest recording at your current settings. At 128 kbps, 25 MB is about 26 minutes. Email attachments are encoded for sending and become larger than the file on disk, so leave some margin under the limit.
Q.Is a FLAC file smaller than the uncompressed result?
A. Usually, yes. FLAC compresses audio without losing any data, so a FLAC file normally takes less space than the uncompressed PCM size this tool shows. For FLAC or ALAC, treat the result as an upper estimate. The tool does not model how much a lossless codec saves, because that depends on the audio.
Q.Why does my computer show a different size?
A. Some programs count 1 MB as 1,000,000 bytes and others count it as 1,048,576 bytes. Use the Size units setting to switch between the two. Tags, headers, and variable bitrate encoding can also move the real size slightly away from the estimate.
Q.Does this tool upload my recording or settings?
A. No. You never select an audio file here. The calculation runs in your browser from the numbers you enter, and nothing is sent to a server.
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