All you have to do is ask…

I was at CompUSA yesterday, shopping for a new sound card as the line in input on mine seems to have pooped out. I walked by the hard drive section and saw a 120GB drive for $59.99. I couldn’t pass that up. I installed it and noticed that the drive had 111GB. I e-mail Seagate’s technical support…


What seems to be missing space on the hard drive is actually the difference between the two numbering systems used in the computer industry.

Decimal vs. Binary

Most Hard drive manufacturers use DECIMAL numbers to show capacity:

(1 KB = 1,000 bytes)
(1 MB = 1,000,000 bytes)
(1 GB = 1,000,000,000 bytes)

Most Computers (BIOS) and Operating Systems use BINARY numbers to show capacity:

(1 KB = 1024 bytes)
(1 MB = 1,048,576 bytes)
(1 GB = 1,073,741,824 bytes)


Seagate’s Model … ST380021A … total formatted capacity expressed in:

The same drive will show up in Windows expressed in BINARY as approximately:
BINARY = 74.5 GB.

Use this formula to convert the DECIMAL 80 GB to a BINARY number

800,000,000,000 GB … divided by … 1,073,741,824 = 74.5 GB

Your Operating System would show this 80 GB drive as a BINARY number equaling 74.5 GB … minus any space already used.


You are NOT missing any space on your Seagate hard drive.

Your Operating System is converting the DECIMAL number and displaying it as a BINARY NUMBER.

If you care to delve deeper into this subject, there is an excellent article regarding this subject at this link:

Robert H.
Seagate Technical Support

========== Customer’s original message ==========

I purchased a Seagate 120GB Barracuda ATA hard drive at a CompUSA in Austin, TX this morning. PN: 9W2883-337 S/N: 3JT20400. I installed the drive but it says there are only 111GB. Where did the other 9GBs go?

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