File size of QuickTime screen video recording

ok, here goes.

to record the mac's internal sound with quicktime you need additional software. i use the free BlackHole Virtual Audio Driver. then you can choose "BlackHole 2ch" in the recording options instead of "Built-in Microphone."

you will also need to set up a multi-output device in your audio MIDI setup utility to be able to both hear and record the internal audio at the same time.

to set up a multi-output device:

Open Audio MIDI Setup: (found in /Applications/Utilities)

hit the '+' button in the bottom left corner and select "Create Multi Output Device"

then in the panel that appears on the right, in the Multi-Output Device tab, select "Built-in Output" AND "BlackHole 2ch". (and, if you want, any of your other connected devices.)

once you do that, (and BEFORE recording) you can choose "BlackHole 2ch" or "Multi-Output Device" in your menubar "sound options". 

to both hear the speakers and record the audio at the same time, choose "Multi-Output Device". before choosing multi-out, set the internal speakers' volume to a comfortable level first. you cannot control the volume once you are in multi-out mode.

have fun. :)

sorry, there is too many variables to give you a set answer to that question. it depends on many factors. among those is:

--the physical size of your screen

--the resolution your display is set to

--the resolution of the video you are recording

--wether you are recording the full screen, or a selected portion of the screen

as an example, i recorded the spacex dragon crew 1 launch. it was 4.5 hours. i recorded it in full screen on my 27" 5K iMac and the video source was at 1080i. it turned out to be 85GB in size. as you can see, you'll want to invest in a bunch of external storage because you will fill up your internal drive quickly if you use it to store your videos.

as a footnote, if you are planning to record the internal audio from those recordings, you'll need additional software. let me know and i'll give you step-by-step instructions to set it up if you need it.