Why advertise it's a 320GB HDD when it only is a 300GB HDD?

It’s some sort of technical loophole all hard drive companies use. You always get approximately 93% of the advertised size.

My computer was sold as a 640 gig but is actually 590-something. My external terabyte drive is actually 931 gigs.

http://www.dslreports.com/faq/9716

320 gigabytes (GB) is shorthand for 320,000 megabytes MB. But a GB is actually 1,024 MB, not 1,000.

320,000 / 1,024 = 312.5. So I would expect 312.5 GB total

I suspect there is hidden partition for the system taking up the other 14.5 GB.

Update: My math is not quite right, @johnpowell‘s link shows the divisor is 1.048576.
320,000 / 1048.576 = 305.2 So I would expect 305.2 GB

When contemplating hard drive sizes from a computer science viewpoint:

1GB = 1,024MB = (1,024×1,024)KB = (1,024×1,024×1,024) Bytes.

So:

320GB = 320x(1,024×1,024×1,024) = 343,597,383,680 Bytes

While that might be what we’d expect to see, that’s not what @sandystrachan got.

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The problem here is that the box is reporting the size from a marketing perspective, relying on Base 10 definitions for “kilo”, “mega”, and “giga”.

The box @sandystrachan‘s hard drive came in is using:

1GB = (1,000×1,000×1,000) Bytes

So:

320GB = 320x(1,000×1,000×1,000) = 320,000,000,000 Bytes.

What happens then, is that your computer (PS3) takes that marketing number and applies the Base 2 math to it (a.k.a. computer science perspective).

320,000,000,000 Bytes ÷ (1,024×1,024×1,024) = 298GB.

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So, @sandystrachan, you do have full access to and use of every single byte advertised on the box. It’s just up to how “giga” is interpreted.

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When Apple released the Snow Leopard (10.6) version of Mac OS X, they set up the OS to report the disk size based on the marketing perspective. Put that 320GB drive into a Mac running Snow Leopard and it’ll show up as 320GB in size. They do not do that with other devices, like anything powered by iOS. (Source).

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@jatkay, if you attempt to use a single simple divisor to figure this out, bear in mind that you’ll need to use a different number each for “kilo”, “mega”, “giga”, “tera”, etc. as they each apply another 1,024 multiplier.

Not only is there some funny math going on here, there is also the fact that many companies like to put in some sort of hidden “recovery” partition to save the cost of including an install disc.

@jerv XD