Bits, bytes, and their multiples

Posted on January 16, 2023, by Sébastien


This post covers the absolute basics, and is aimed at people who aren't familiar with these concepts (yet).


The bit is the smallest unit of information.

It has only two possible values: 0 or 1.

The symbol for the bit is either simply "bit", or the lowercase letter "b".


A byte consists of eight bits.

It's represented by the uppercase letter "B".

Capitalization is crucial, as the lowercase letter "b" represents the "bit" unit, as mentioned above.

Multiples (powers of 10)

Strictly speaking, the "kilo" prefix denotes one thousand – as in "kilogram" or "kilometer" – "mega" is one million, "giga" is one billion, "tera" is one trillion, and so on.


Again, capitalization is important:
Interpreted literally, 1 mb/s would be 1 millibit per second.
That is to say, 0.001 bit/s, instead of the intended 1,000,000 bit/s (1 Mbit/s).

Multiples (powers of 2)

Sometimes, multiples of 1024 are used instead of multiples of 1000.
This number was chosen because 1024 is a power of 2 (namely, 2¹⁰).

Strictly speaking – again – multiples of 1024 should use different prefixes than multiples of 1000:

However, there's a catch:

Operating systems such as Windows use the metric prefixes… to represent binary multiples!

This can lead to some confusion:

Common uses of bits, bytes, and their multiples

A note about internationalization

In some languages, the word "byte" is not used, and a different letter may be assigned to represent it.

In particular, the French word for "byte" is "octet", and the symbol is "o".

This causes quite some confusion when a native French speaker sees a label such as "32 GB" for the first time (on a USB flash drive, typically).
They might think they received a 32 gigabit device, which would be 8 times smaller than the 32 gigabytes they wanted ("32 Go").