Prefixes for counting large numbers
A bit is a binary digit that can have the value 0 or 1. All computer data is made up of suitably encoded bits. A large file or message has many bits, a small file few.
- A kilobit is 1,024 bits.
- A megabit is 1,024 * 1,024 = 1,048,576 bits.
- A gigabit is 1,024 * 1,024 * 1,024 = 1,073,741,824 bits.
- A terabit is 1,024 * 1,024 * 1,024 * 1,024 = 1,099,511,627,776 bits.
After these prefixes come peta, exa, zetta and yotta. The pattern continues -- each is 1,024 times the previous one.
The prefixes kilo, mega, giga and tera signify a thousand, million, billion or trillion. For purposes of making estimates in our class -- quick calculations -- we can use 1,000 instead of 1,024. If we do that:
- A kilobit is 1,000 bits (one thousand).
- A megabit is 1,000,000 bits (one million).
- A gigabit is 1,000,000,000 bits (one billion).
- A terabit is 1,000,000,000,000 bits (one trillion).
Since there are 8 bits in a byte, you can easily convert from the number of bits in a file or message to the number of bytes and vice versa.