Pro Tools 101_ An Introduction to Pro Tools 11 ( PDFDrive )

Pro Tools records all audio using sample rates ranging from 44.1 kHz to 192
kHz, with bit depths of 16-bit, 24-bit, or 32-bit floating point. At a sample
rate of 44.1 kHz, each track consumes approximately 5 megabytes (MB) of
disk space per minute for 16-bit audio (mono), 7.5 MB per minute for 24-bit
audio (mono), and 10 MB per minute for 32-bit floating point audio. With
increasing bit depth and sample rates, hard disk space consumption increases
correspondingly; recording at a sample rate of 88.2 kHz, therefore, consumes
twice as much space as recording at 44.1 kHz. Similarly, recording in stereo
consumes twice the space of recording in mono.
Table 3.1 in Lesson 3 shows approximate storage consumption at the
different data rates supported by Pro Tools.
Tip: Pro Tools audio files require a small amount of additional disk
space to store associated clip metadata; this can add up to 0.3 MB
per minute to the total file size.
Calculating File Sizes
The sample rate and bit depth of the audio you record are directly related to
the size of the resulting files. In fact, you can calculate file sizes in
mathematical terms using these two parameters:
Sample Rate × Bit Depth = Bits per Second
Or, stated another way:
Sample Rate × Bit Depth × 60 = Bits per Minute
In the binary world of computers, 8 bits make a byte, 1,024 bytes make a
kilobyte (KB), and 1,024 KB make a megabyte (MB). Therefore, this
equation can be restated as follows:
(Sample Rate × Bit Depth × 60) / (8 bits per byte × 1,024 bytes per
kilobyte × 1024 kilobytes per megabyte) = Megabytes (MB) per Minute
Reducing terms gives us the following:
Sample Rate × Bit Depth / 139,810 = MB per Minute
So by way of example, recording audio at a sample rate of 44,100 samples
per second with a bit depth of 24 bits per sample would generate files that
consume space at the following rate:
44,100 × 24 / 139,810 = 7.57 MB per Minute