Why Hard Drive Show Lesser Available Space

The Mystery of Stolen Disk Space

It all started with my new laptop. I had bought my laptop customized, with every part chosen carefully. When it came to the hard drive, I settled with a lesser capacity drive, only because I wanted a 7200 RPM drive. I chose the one with highest capacity 7200 RPM drive, which of course was considerably “smaller” when compared to the “regular” 5400 or 4200 RPM drives.

With a big smile on my face, I booted my laptop for the first time. The smile went away quickly, when I noticed that Windows reported the total disk space lesser than what I had ordered. My first thought was it must be the System Reserved space. I opened the Disk Management, and was frustrated further to find that System Reserved space was only 100MB, while I was short of few GBs.

I started digging deep. The truth that came out was shocking and irritating. The root of all this different interpretation of the “kilo”. Most of us know that a kilo means a 1000. For example, a kilogram has 1000 grams. When it comes to the “computer stuff”, a kilo is 1024. So a kilobyte would mean 1024 bytes. Right?

Now this different interpretation of kilo is used by the hard drive makers very intelligently to fool people like us. If you read carefully on the box of a hard drive, they do mention that 1kb=1000b. As expected, no one bothers to read the fine print. So, Windows calculates a kilobyte as 1024 bytes, while hard drive makers calculate a kilobyte as 1000 bytes. Confused? Here is a proof:

Hard drive makers sell a 500GB drive. With the calculation factor of 1000, the number of bytes would be:

500GB x 1000 X 1000 X 1000 = 500,000,000,000 Bytes

When Windows calculates the space, it used 1024. So the same disk space is calculated as:

500,000,000,000 / 1024 / 1024 /1024 = 465 GB

See? 35GB gone! See the screen print if you still don’t believe. (And yes, you can read more about this 1000 vs 1024 calculation at https://en.wikipedia.org/wiki/Kilobyte)

Stolen Disk Space

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