How to calculate the capacity of Computer Hard Disk Drives

Readings capacity hard disk on a system, often or even always, not in accordance with the capacity indicated on the physical hard disk. For example, a hard disk capacity of 80 GB of physical, will be read as 74.5 GB (or less) after formatted.
The greater the capacity of the hard disk, the greater the capacity of the "missing". Actually, this is a natural thing.

But if we do not know how to calculate the correct hard disk capacity, then we will be confused with the "lost" his capacity of the hard disk.
As quoted from the web western digital hard drive manufacturers use the decimal system to calculate the capacity of hard disks produced.

• 1 MB = 1,000,000 bytes.
• 1 GB = 1,000,000,000 bytes.
• 1 TB = 1,000,000,000,000 bytes.

Bytes is the smallest size in units of computer capacity, and for a while it terrabytes (TB) is the largest unit that is found in today's hard disk capacity.
Let us count
While on the windows, the system reads 1 KB = 1024 bytes, 1 MB = 1024 KB, and so on.
I do not multiply calculations here as above, so it is easy to read. Thus, if a hard disk capacity of 80 GB, then:
"Plant capacity = 80GB x 1,000,000,000 = 80,000,000,000 bytes".
Capacity in the system (calculated sequentially from the smallest capacity):

• 80,000,000,000 / 1024 = 78,125,000 KB
• 78,125,000 / 1024 = 76.293,94531 MB
• 76.293,94531 / 1024 = 74.50581 GB

Thus, a hard disk capacity of 80 GB of physical will be read as 74.5 GB (approximately) when read by the system.