A kilobyte is 1024 bytes. Exactly.


Unfortunately, it’s never that simple.

In reality, a kilobyte can also mean 1,000 bytes. Exactly.

Because the prefix “kilo” actually means 1000 in systems used more often by humans than computers (like the metric system),  people tend to use it as 1000 in tech, too. For example, a kilometer is 1,000 meters.

And, let’s face it, it’s easy to think of a kilobyte as “about” 1000 bytes.

Why 1024? Because computers think only in powers of two; when you think that way, that’s a “round number”. In binary, 1024 is represented as a one followed by 10 zeros (10000000000): a round number when you think only in powers of two.

1000 is a round number to us, but to computers, 1024 is 1111101000: not very “round” at all.

Why one followed by 10 zeroes instead of one followed by, say, 9? Basically because 1024 is closer to our more common definition of “kilo” being 1000 than 512 is.

But wait, it gets worse. The geek powers that be have created a new word – kibibyte – which means 1024 bytes and only 1024 bytes, to remove the ambiguity that is kilobyte.

It’s not catching on very quickly.

kilobyte (Wikipedia)
Multiple-byte units
Value Metric
1000 kB kilobyte
10002 MB megabyte
10003 GB gigabyte
10004 TB terabyte
10005 PB petabyte
10006 EB exabyte
10007 ZB zettabyte
10008 YB yottabyte
Value IEC Memory
1024 KiB kibibyte KB kilobyte
10242 MiB mebibyte MB megabyte
10243 GiB gibibyte GB gigabyte
10244 TiB tebibyte TB terabyte
10245 PiB pebibyte
10246 EiB exbibyte
10247 ZiB zebibyte
10248 YiB yobibyte

The kilobyte is a multiple of the unit byte for digital information.

The International System of Units (SI) defines the prefix kilo as 1000 (103); per this definition, one kilobyte is 1000 bytes. The internationally recommended unit symbol for the kilobyte is kB.

In some areas of information technology, particularly in reference to solid-state memory capacity, kilobyte instead typically refers to 1024 (210) bytes. This arises from the prevalence of sizes that are powers of two in modern digital memory architectures.

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