Working with bits and bytes and everything in between can be confusing if you aren’t familiar with how it all works. If you wanted to know why your hard drive is actually a lot smaller than what is written on the box and that’s considered fair game, read on. If you just want a go-to guide to send to your friends, then this guide is also for you. Hopefully this can clear up all the incorrect usage of terms on the internet once and for all! And yeah, I know I’m dreaming…

## Bits

**Definition**:** **1 bit is the smallest divisible amount of digital data. One bit will be either represented by a 0 or 1 in binary: on or off.

**Abbreviation**: b

## Bytes

**Definition**: 8 bits of data form one byte. Bytes are the most commonly referred to unit in digital storage.

**Abbreviation**: B

## SI Prefixes

**Definition**: The SI (from the French **S**tandard **I**nternational) units are prefixes which multiply the value of bits or bytes. It is a base 10 system.

**Abbreviations**:

Prefix | Symbol | 10^{n} | English Name | Number |

Kilo | k | 10^{3} | Thousand | 1,000 |

Mega | M | 10^{6} | Million | 1,000,000 |

Giga | G | 10^{9} | Billion | 1,000,000,000 |

Tera | T | 10^{12} | Trillion | 1,000,000,000,000 |

Peta | P | 10^{15} | Quadrillion | 1,000,000,000,000,000 |

Exa | E | 10^{18} | Quintillion | 1,000,000,000,000,000,000 |

## Base 2 Prefixes

**Definition**: These prefixes are used almost exclusively in computer science to account for the fact that computers inherently work on a base 2 system rather than a base 10 system.

**Abbreviations**:

Prefix | Symbol | 2^{n} | Number |

Kibi | Ki | 2^{10 } | 1024 |

Mebi | Mi | 2^{20} | 1,048,576 |

Gibi | Gi | 2^{30} | 1,073,741,824 |

Tebi | Ti | 2^{40} | 1,099,511,627,776 |

Pebi | Pi | 2^{50} | 1,125,899,906,842,624 |

Exbi | Exi | 2^{60} | 1,152,921,504,606,846,976 |

## Working with Units

It is relatively simple to combine the prefixes with bits or bytes if you remember the scales. Let’s consider a few examples:

1KB = 1 kilobyte

1Kb = 1 kilobit

1Mb = 1 megabit

1KiB = 1 Kibibyte

1Tib = 1 Tebibit

When working with the commonly used SI prefixes, each “step up” is 1000 times larger than the previous one:

1000B = 1KB

1000KB = 1MB

1000MB = 1GB…

It is common to use **bits** when referring to networking applications, while most other uses will normally be presented in **bytes**. For example:

Network adapters are commonly 100 Mb/s (100 mega**bits** per second)

Hard drive capacities now reach up to 2 TB (2 tera**bytes**)

Converting from bits to bytes is equally simple; all you need to know is how to divide by 8:

Uncapped, ADSL can reach up to 8 Mb/s (8 mega**bits **per second)

This is equivalent to 1 MB/s (1 mega**byte** per second as there are 8 bits per byte)

Another case where proper usage of terms can be confusing is with HDD capacities; the reason that your 1 terabyte hard drive does not format to a full 1000 gigabytes is because they are rated using the SI base 10 system, while computers actually work on a base 2 system. For example, see the conversion done in Wolfram|Alpha.

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