Loss hard disk space after reformatting?

[Rob Black]

Hi,

I recently purchased a 250 USB external hard drive for my Mac, I formatted the HDD and I ended up with 233.56GB of disk space. Thats quite a loss. Is this normal to loose that much space after formatting?

Thanks in advance.

 

[Kueller]

1 gigabyte = 1,073,741,824 bytes
250GB / 1.073741824 = 232.83gigabytes

Q: I ordered a 40 GB hard drive and OS X is telling me that it is only 37.3 GB. Did I get ripped me off?

A: What you are seeing is not really a problem at all, but actually a discrepancy in the way drive sizes are reported. Hard disk manufacturers use decimal megabytes (1,000,000 bytes) in their advertising, and BIOS auto-detect routines use the same measure. Other software, especially most disk setup and partitioning utilities use binary megabytes (1,048,576) in their reporting. A Decimal GB is reported as 1,000,000,000 bytes and a binary GB is reported as 1,073,741,824 bytes. The difference of about 7% is what you are seeing.

According to the disk manufacturer, your 40 decimal GB hard drive has 40,000,000,000 bytes. Your software uses the binary system to measure with so 1 GB in the binary system is 2^30 bytes or 1,073,741,824 bytes. If you take the 40,000,000,000 that the manufacturer says the drive has and divide it by how your software measures GB (1,073,741,824 bytes), you end up with 37.2529 GB using the binary system.

So you are not missing anything and you were not ripped off.

 

[Oldie]

This link explains it well.

http://www.discinterchange.com/TechTalk_gigabytes_.html

Basically MS Windows, and the drive manufacturer calculate the space on storage devices differently. The descrepancy causes Windows to see a drive as smaller than the advertised space. You're certainly not the first, or the last, to see this practice as unfair; but it's not going to change soon. You are in fact getting the advertised amount of space, per the documentation on the box.