How to calculate video size?

[Guest]

I have a 30 minute video here and I need to know what the outcome file size will be.

it's 512 x 512, each pixel is 6 bits and I want to render in 24fps. Do I multiply all of this together? It doesn't really give me a number I can regcognize

[Harm_Millaard]

30 (minutes) x 60 (seconds) x 24 (FPS) x 6 (BPC) x 3 (RGB or 4 x for RGBA) x 512 (horizontal dimension) x 512 (vertical dimension). This is in bits, not bytes.

But I don't think you can export with 6 BPC, only with 8 or 10.

[Todd_Kopriva]

Here's a page that has some additional information beyond Harm's answer:

"Storage requirements for output files"

[Jim_Simon]

File size is calculated simply using duration x bitrate.  Other things like frame rate, dimensions and bpc will have little effect.

[Colin_Brougham · Accepted solution]

File size is calculated simply using duration x bitrate.  Other things like frame rate, dimensions and bpc will have little effect.

It ain't necessarily so.

While that is true if you are exporting to a format and codec that has variable bit rates, if you are using an uncompressed format or a lossless codec (like Lagarith, for example), those other elements--frame rate, dimensions, and bit depth--are primary factors in file size.

For example, I just did a quick test using 6 seconds of a simple red solid matte in a 24p sequence, exported using Microsoft AVI/None in three different frame sizes. Here's the results:

100x100: 4,407 KB

512x512: 115,212 KB

1920x1080: 911,262 KB

Huge differences, due to just one of those other factors. However, when using something like MPEG-2 or H.264, you can control the bitrate, and each of those three encodes would be pretty similar in file size.

Jim--I know you know all this, but I just thought it prudent to point out that there are those other factors to consider when dealing with certain encoding scenarios.