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Gigabytes, Kilobytes and Bytes Explained

Hard Drive Capacity

Hard DrivePeople are often confused when they buy a new computer as the amount of space shown on their PC's hard drive is always less than the amount they expect. Why is this?

When you buy a computer or a new hard drive you might go for a 500 GB drive or a even a Terabyte (1000 GB) drive but your Windows PC will only report 4696GB or 931GB respectively. Why do drives seem to shrink once they added to a computer case?

While most manufacturers of hard disk drives and flash drive devices define 1 Gigabyte as 1,000,000,000 bytes, operating software like Microsoft Windows reports the size in Gigabytes by dividing the total capacity in bytes by 1,073,741,824, while still reporting the result with the symbol GB.

This practice is a cause of confusion, as a hard disk with a manufacturer-rated capacity of 750 GB will usually be reported by the Windows Operating System as only "698 GB" (other software, like Mac OS X 10.6 and some components of the Linux kernel measure using decimal units).

The problem here is that a Kilobyte does not equal 1,000 individual bytes, it is 1,024 bytes. Because these two values are so close drive manufactures will advertise a nice rounded up figure such as 500GB or 750 GB. But to a computer, a kilobyte is always 1024 bytes. And a single Gigabyte is therefore 1,073,741,824 bytes. Test this in our bytes converter and see for yourself the true value of 1 Gigabyte.

Note: The reason you see less is not due to the Windows Operating System as this reduction happens even if a disk is completely clean and has no operating system on it whatsoever. It happens because manufacturers insist on using round numbers that show you have more hard drive space than you actually have.

The True Drive Capacity

Perhaps a few examples will make things a bit clearer.



1 Kilobyte (KB) 1,024 bytes
1 Megabyte (MB) 1,048,576 bytes
1 Gigabyte (GB) 1,073,741,824 bytes
1 Terabyte (TB) 1,099,511,627,776 bytes
1 Petabyte (PB) 1,125,899,906,842,624 bytes

So to convert the manufacturers inflated GB value into the Windows PC's equivalent GB value just divide the inflated figure by 1,073,741,824 i.e. a 700GB hard drive is really 700 divided by 1,073,741,824 which equals 652GB.

A 500 GB hard drive is therefore 500 divided by 1,073,741,824 which equals 466 GB and a 1TB drive will be 1024 (1024 GB equals 1 Terabyte) divided by 1,073,741,824 which equals 954.

See our bytes converter to find the number Kilobytes in a Megabyte or in a Gigabyte or even in a Terabyte and get a complete understanding of their relationship.

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