How to basically calculate the number of GB needed to save a 1 hour Streaming Broadcast?

I have Audacity 2.4.2
I have Windows 10
I found a audio broadcast posted by a streamer on
I want to be able to record it on my laptop computer using Audacity
I do not know how may Gigabytes one hour of the recording is going to require
Eventually I am going to have to save it to a flash drive
I am not technically savvy enough to understand how to convert Bitrate to hours needed
although I did watch a Youtube video on the subject
I’m just not too confident about figuring this out using the formula expressed on YouTube
I am just interested in getting a general understanding of things
In other words, if the streamer on Twitch has an audio broadcast equal to an hour than how many gigabytes will I need to record it to a Flashdrive?
I want those at Audacity to know how grateful I am as an occasional end user. The software is terrific, at least, when I remember how to use it.
Please remember, I am only moderately tech knowledgeable. I just interested here in a general guideline.
I wish there was a way to give you some of the pistachios I’ve been munching on while trying to type out this question. But it’s the thought that counts.

This table from the Audacity Manual should help you:


Audacity records in a super-high quality format (32-bit float PCM) which requires a lot of disk space.
Assuming that you are using default setting (32-bit float, 44100 Hz sample rate, stereo):
1 sample = 4 bytes (one channel)
1 sample = 8 bytes (stereo)
1 second = 8 x 44100 = 352800 bytes = 352.8 kB
1 minute = 352.8 x 60 = 21168 kB = 21.168 MB
1 hour = 21.168 x 60 = 1270.08 MB = 1.27008 GB

So for stereo, about 1.3 GB per hour, or 0.65 GB (635 MB) for 1 hour mono.

You would normally export (to create a normal audio file) in a less extreme format.

A normal, CD quality, stereo WAV file = 635 MB per hour
A normal, CD quality, mono WAV file = 317.5 MB per hour

CD quality FLAC file (stereo) = about 400 MB per hour

For lossy (inexact) compressed formats such as MP3, OGG, AAC, WMA and the rest, the file size depends on the quality settings. Typically the file size will be between 1/4 and 1/10 of the size of a WAV file.

An hour at perfect quality WAV (Microsoft) 16-bit (Stereo CD Quality) comes in at 635 MB.

That’s the base-line quality I use for everything unless there’s a reason not to. Internet services are almost always compressed and squashed to a lesser quality, sometimes much less, but storing them in CD quality insures that I won’t make the quality any worse.

Any of the other file types except a couple of the lossless formats will cause sound quality errors. I don’t use the other lossless formats because they’re special purpose formats and not everybody can deal with them. WAV will open up on all three computer platforms and play perfectly. I deliver WAV to my commercial clients and never had a complaint.

If you don’t have room for that, your job is to decide how much sound damage you’re willing to accept.

There is one oddity you might want to know about. MP3 and other compression techniques are little time bombs waiting to go off later. People who download internet music and then use them in productions are horrified when their customers make MP3 files for running-on-the-beach personal music players and the music turns to honky trash. Multiple compressions have caught up with them.

There was a producer in New England who got stuck with this compression problem. He used internet MP3s in his production and then delivered to the radio station in MP3. The radio station broadcast it OK, but then couldn’t make their podcast. The music turned to trash. The solution was deliver to the station on actual CDs. No compression.


Steve: Thank you for taking the time to explain this to me. You certainly did a fine job explaining how you calculate things. And I am grateful.

kozikowski: I also thank you for your imput on my question.

In general, I may not completely understand everything both of you wrote about as a Techie Knowledgeable People (Aka: Space Robotics Technicians (LOL) ), but I have a general idea of how to handle my problem now. Thank you.

So, if I am lucky then 1 CD-R that is rated at: 52x | 700 MB | 80 min
by your calculations:
So for stereo, about 1.3 GB per hour, or 0.65 GB (635 MB) for 1 hour mono.
635 MB = 1 hour mono
Which means, I should be able to use 1 CD-R per hour of a broadcast I want to copy from Twitch.
Gee, I sure hope I am right. But folks, this for me is a real hassle. I am trying to both learn and apply things.

Again, thank you. If I run into any more questions then I’ll let you folks know.

So for stereo, about 1.3 GB per hour, or 0.65 GB (635 MB) for 1 hour mono.

Close. That higher number is for Audacity’s super high internal format.

But down here in the real world:

From Steve:
A normal, CD quality, stereo WAV file = 635 MB per hour

From Koz:
An hour at perfect quality WAV (Microsoft) 16-bit (Stereo CD Quality) comes in at 635 MB.