Understanding Gigabytes

March 8, 2008 – 7:11 PM

When people buy computers, they’re told they’re getting a hard drive of a certain size–80 gigabytes, perhaps. But when they check the computer they find only 74GB. Where did the other 6GB go? This is the difference between marketing and math. As far as marketers are concerned, 80 billion bytes is 80GB. But it’s not. A gigabyte is 1.074 billion bytes (2 to the power of 30). If you divide 80 by 1.074, you’ll get 74.6. That’s the true number of gigabytes.

These round numbers are fairly easy to remember. A kilobyte is 2 to the power of 10 (or 2^10), a megabyte is 2^20, and a terabyte (1.0995 trillion bytes!) is 2^40.

Few people are going to fill up that so-called 80GB drive, regardless of the stated size. Still, I wish marketers were more honest about hard drive sizes. It should be easy to understand what you’re really getting.

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