Well recently I was asked the question “Why, when i buy an 80GB drive, does it only see around 74GB in the OS? Thats like 6GB lost!”.

Simply put, It’s base10 vs base2; or as a colleague of mine would say, “we arent comparing apples with apples”. There are 2 different methods used to calculate how much information can be stored on the hard disk drive. They are base-2 system and the base-10 system.

In the base-2 system used by the OS, 1GB = 1,073,741,824 bytes. While the base-10 system used by the manufacturing company, 1GB = 1,000,000,000 bytes. Here we begin to see the “1GB vs 1GB” discrepancy already. Now amplify it, and you begin to understand where your 6GB is 🙂

Here is a good reference table I found on the internet a while back:

Base 2        Base 10

————————–
80 GB        76.3 GB
120 GB      114.4 GB
160 GB      152.6 GB
250 GB      238.4 GB
1000 GB    953.7 GB

Hope this helps clarify things!
Sam