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Kilobytes, Megabytes, and the Metric System

To understand how we measure data is to understand the metric system, which unfortunately is not a given in the United States of Inches and Feet. Our documents, photos, videos, and apps are all measured in bytes—the virtual building blocks of our data.
These days our files are too big to be measured in only bytes—a Blu-Ray disc, for example, holds 10 billion bytes of data—so we use the metric system to make the language more understandable. 1,000 bytes is a kilobyte*, 1,000 kilobytes is a megabyte, and so on.

Kilobytes and megabytes were large units of data measurement in the past, but now technology has moved on and consumers are now using gigabytes and terabytes, and perhaps in the not-so-distant future will start using petabytes.

*A kilobyte is actually 1,024 bytes, but for the sake of understanding the system, we’ll talk in intervals of 1,000.

Gigabytes (GB)

IBM built the first gigabyte hard drive in 1980, weighing 550 pounds and costing $40,000. But the first true gigabyte drive that people could and would actually buy was introduced in 1991 and remained the standard “large” until until the 2000s. A gigabyte is 1,000 megabytes and we still measure a lot of files that way today; movies, TV shows, video games, and apps are all measured in some range of gigabytes:

•     A movie at basic TV quality (480p) is 1 GB
•     A standard DVD holds 4.7 GB
•     A Blu-Ray disc holds 10 GB
•     Battlefield 4 for Xbox One is approximately 34 GB
•     A good solid state drive is around 250 GB

Terabytes (TB)

Fast forward to 2007 and Hitachi brings us the world’s first terabyte hard drive for consumers. Following the metric system, a terabyte is 1,000 gigabytes and it’s the unit in which we measure almost all modern hard drives. In fact, a hard drive is considered a letdown if it’s anything less than 1 TB. That’s why everyone wants the 1 TB versions of the Xbox One and Playstation 4 over the 500 GB hard drive. Even solid state drives are starting to produce in 1 TB, and the biggest consumer drives available are only made in 10–12 TB (and they’re very expensive).

•     212 DVD-quality movies or 125 Blu-Ray quality movies is 1 TB
•     Most “large” hard drives today are 2–4 TB

Petabytes (PB)

There’s no such thing as a mass-market petabyte drive and there won’t be for a long time. A petabyte is 1,000 terabytes and that is huge. Only data centers and some large IT servers measure in petabytes:

•     All US academic research libraries is 2 PB
•     The production of every consumer hard drive is 20 PB
•     All the printed material in the world is 200 PB

And finally, as a footnote, there is the exabyte—1,000 petabytes—which is so large we likely won’t see an exabyte drive in our lifetime. Just to understand the scale, every word ever spoken by human beings is 5 exabytes. Even if you wanted to own every movie and TV show ever made in ultra-high 4K resolution, you wouldn’t come close to filling an exabyte in your lifetime. Wow!