Podcast Audio File Size Calculator
Enter your episode length and encoding settings to see the exact file size in MB, your monthly bandwidth at any download count, and how much hosting would cost. Pick the right bitrate before you upload. Nothing uploaded.
Episode settings
Encoding settings
Results
Bitrate comparison - same duration, all bitrates
| Bitrate | File size | Monthly bandwidth | Monthly cost |
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Learn more: podcast file size math
Compressed formats
For MP3, AAC or OGG at a constant bitrate, size is bitrate in bits per second divided by 8, times the duration in seconds. A 60-minute episode at 128 kbps is 128,000 / 8 x 3,600 = 57,600,000 bytes. The tool shows that as 54.93 MB, because it divides by 1,048,576 bytes.
Wikipedia's megabyte article explains the gap. A megabyte is one million bytes by SI standards, while the binary unit, the mebibyte, is 1,048,576 bytes, and Windows and some other systems label that as MB. So the tool's MB is the binary one. The 64 kbps version of the same episode is 27.47 MB, half as much.
Channel count does not change a compressed file at a given bitrate. A stereo and a mono MP3 at 128 kbps are the same size. A mono file only saves space if you also lower the bitrate, for example 64 kbps for mono voice against 128 kbps for stereo.
Lossless formats
WAV and AIFF are uncompressed. Size is sample rate x bit depth / 8 x channels x duration. An hour at 44.1 kHz and 16-bit is 635,040,000 bytes (605.6 MB) in stereo and 302.8 MB in mono. Here the channel count does matter, and mono is half the size.
Wikipedia says FLAC can typically reduce audio to between 50 and 70 percent of its original size, and that it decompresses to an identical copy. The tool assumes 55%, so the stereo hour comes to 333.1 MB. The real ratio varies with the recording.
Mono for a solo voice
For a single speaker on one microphone, a stereo file usually carries the same signal in both channels. A mono lossless file is then half the size with the same content. That is a different matter from music or a multi-microphone mix, where the stereo image carries information.
Bandwidth cost and duration input
The monthly figure multiplies the file size by your downloads, converts to GB and prices it at a flat 1 cent per GB. That is the tool's own rate and not a host's price, so replace it with your host's pricing. At 10,000 downloads of the 54.93 MB episode, that is 536.4 GB and about 5.36 dollars.
The duration box takes hh:mm:ss, mm:ss or plain minutes, so 45:30 is 45 minutes 30 seconds, 1:05:00 is an hour and five minutes, and 90 is 90 minutes. Sizes assume a constant bitrate. A variable bitrate file will differ.
FAQ
What bitrate should I pick for speech?
The tool's options run from 64 to 320 kbps, and it shows what each one costs in size and bandwidth. 128 kbps gives about 55 MB an hour. Listen to a short sample at your candidates and choose the lowest one that sounds good to you.
Does sample rate matter for MP3 size?
No. For compressed formats the tool uses bitrate only. Sample rate and bit depth are multipliers for WAV, AIFF and FLAC.
How is the monthly bandwidth worked out?
File size times monthly downloads, converted to GB and multiplied by the tool's flat 1 cent per GB. It is a rough estimate, since hosts price bandwidth and storage in many different ways.