Harddrives size different then listed?

[[CaM]Spoon]

Hi guys just wondering i know when you buy like a 250 gig harddrive its usuallly random and might be up to 10 gig less. I have 74 gig raptor and it reads as a good old 69er. Then theres a 160 that reads asn 153. Just wondering i just picked up a 250 and its reading as a 232, is that normal?
Why is it off so much?
does this mean if i buy a 500 gig it will be a 450?

 

[444]

There's two things:

Two definitions of gigabyte, gb and GiB: 1024MB vs 1000MiB
Computers display the 1024 version, HD companies use 1000 version.

Formatting incurs some overhead, the filesystem takes some space too.

 

[TeeJayHoward]

232.8GB or whereabouts is correct. A 500GB should be 456.6GB.

Quick and dirty way to find out the "real size" of your drive:

Advertised Size * 0.93 = Real Size
(Actually, it's .931322574615478515625, but 0.93 works in most cases )

It doesn't always hold true, however. Some manufacturers don't go by the 1000/1024 setup. For example, my WD 320GB drive is 298GB when formatted. That's "correct". My 160GB Maxtor is 152GB. That's "wrong". It should be 149GB. But I'm not going to complain about an extra 3GB! I got a 163-164GB drive when I paid for a 160GB.

The reason for the 0.93 number is, like 444 said, hard drive companies use a Base-10 system. To convert, you need to change it to a Base-2 system. The formula for doing this is
Advertised Size
*(1000/1024) <----------------to convert to KB
*(1000/1024) <----------------to convert to MB
*(1000/1024) <----------------to convert to GB
___________
Real Size

I find it easier to just type in the number.

An interesting note: I discovered the .93 number by using my WD drive. However, in this post, joeshmo1985 showed me WHY it worked. Prior to this, I assumed the extra space was filesystem overhead, and that just one (1000/1024) was needed. Just gotta give credit where it's due.

 

[General Crespin]

Thanks for that info, TJH! Interesting to see the "why".

 

[Ockie]

This is the reason companies are being sued for false advertising. I don't know the outcome of that case or when the companies have to start complying with the new rules.

 

[unhappy_mage]

My 160GB Maxtor is 152GB. That's "wrong". It should be 149GB. But I'm not going to complain about an extra 3GB! I got a 163-164GB drive when I paid for a 160GB.

The reason is that different manufacturers count differently. So for WD, there may be three 1k/1000 conversions. That drive appears to be using two - 160,000,000 KB / 1048576 = 152.5 GB. So I'd call that 160 million KiB. Seagate seems to label their drives (the ones I have, anyways ) in thousands of MiB. But it's not really important; all I'm saying is the reason is the same.