In short: To estimate a podcast file, multiply the bitrate in kilobits per second by the length in seconds, then divide by eight to get kilobytes. At 96 kbps, a 45-minute episode is about 32 MB. Multiply by the number of episodes for a year of storage, and keep the uncompressed master separate.
A podcast file size is simple arithmetic: bitrate times time, divided by eight. The part people get wrong is the units. Bitrate is measured in bits per second, file sizes are usually given in bytes, and there are eight bits to a byte. Once the units are straight, the sum takes a few seconds.
The formula
Size in kilobytes = bitrate in kilobits per second × length in seconds ÷ 8.
Divide the kilobytes by 1,000 to get megabytes. Operating systems differ on this: some count a megabyte as 1,000 kilobytes and some as 1,024. At podcast sizes the difference is small, so the estimate is good enough for planning.
Worked examples
- One 45-minute episode at 96 kbps: 96 × 2,700 ÷ 8 = 32,400 kilobytes, about 32.4 MB.
- The same episode at 128 kbps: 128 × 2,700 ÷ 8 = 43,200 kilobytes, about 43.2 MB.
- A year of 52 weekly episodes at 96 kbps: 32.4 MB × 52 = 1,684.8 MB, about 1.7 GB.
Work in seconds, not minutes, so the multiplication stays clean. A 45-minute episode is 2,700 seconds.
What changes the number
- Bitrate. This is the main lever. A higher bitrate gives a bigger file, and a lower one saves space at some cost to the detail the encoder keeps.
- Length. Trim silence, false starts and repeated takes first. That is quicker and often cheaper in storage than dropping the bitrate.
- Mono or stereo. The size formula does not change. The bitrate is the total for the whole file, so a mono file and a stereo file at the same bitrate come out the same size. Mono is a separate decision about how the audio is made.
- The master. An uncompressed 16-bit, 44.1 kHz stereo file runs at about 1,411 kbps, roughly fifteen times the 96 kbps example above. Keep the master for editing and archiving, and make the delivery file from it.
Apple Podcasts' audio requirements, read on 5 November 2026, list MP3 or AAC for the RSS feed at 44.1 or 48 kHz, with 64 to 128 kbps for mono and 128 to 256 kbps for stereo. The calculator checks your bitrate against that range for the channel count you choose. A 96 kbps stereo file is therefore below Apple's listed range, while 96 kbps mono is inside it, and the 96 kbps examples above are sums, not recommendations. Other hosts and apps may ask for something different, so check each service you publish to.
The master comparison in the calculator offers two uncompressed WAV masters, 16-bit at 44.1 kHz and 24-bit at 48 kHz.
Common mistakes
- Dividing the wrong way. Bits to bytes is a division by eight. Bytes to bits is a multiplication.
- Treating kbps and kB/s as the same unit. 96 kbps is 12 kilobytes per second, not 96.
- Calculating one episode and forgetting to multiply by the number of episodes in a year.
- Forgetting the master. A delivery file is much smaller than the recording it came from, and you will need the recording again.
- Choosing a bitrate from a forum post without checking what your hosting or distribution service asks for.
Where the calculator fits
Run the calculator once before you export, to check the settings, and again when you plan storage for a season. Keep the editing order in mind as well, because the clean-up and mix happen before the export, and that is when the length is fixed. The editing order of work guide covers that sequence, and the loudness targets guide covers the level side of delivery.
If you would rather hand over a finished episode than work through the export, Granary's Classic podcast package is £395 +VAT per recorded episode, and the edit and files are delivered within five working days. Our podcast production page explains what is included.
Related guides
- Editing order of work: clean, tighten, mix, master
- Loudness targets for podcasts and platforms
- All guides and tools
The picture at the top of this page is an illustration, not a photograph of a client or a real job.
Questions we get asked
What bitrate should I export a podcast at?
It depends on where the file is going. Export a high-quality master and keep it, then check what each platform you publish to asks for before you choose a delivery bitrate.
How do I work out a podcast file size?
Multiply the bitrate in kilobits per second by the length in seconds, then divide by eight. The answer is the size in kilobytes, and you can divide by 1,000 to get megabytes.
Why is my exported file bigger than the calculation?
Usually the export is not the setting you think. Check whether you exported the master or the delivery file, and whether the bitrate is constant or variable, because a variable file changes size as the audio changes.
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