Associated Topics || Dr. Math Home || Search Dr. Math

### Prefix for 10^30 Bytes

```
Date: 05/25/2000 at 15:32:05
From: James Boden
Subject: Prefix Names for Bytes

I need to know what a group of bytes would be called if it were 10^30
bytes. For example: kilo- = 10^3 or 1,000, mega- = 10^6 or 1,000,000,
next is giga- (1,000,000,000) and then tera- (1,000,000,000,000). What
do you call 1,000,000,000,000,000,000,000,000,000,000 or 10^30 bytes?

Thank you.
```

```
Date: 05/25/2000 at 17:08:44
From: Doctor Rick
Subject: Re: Prefix Names for Bytes

Hi, James.

There is no prefix defined for 10^30 yet, and we have no need for it
yet, so there's probably no rush to define one. We use the standard SI
(metric system) prefixes, which you can find in many Web sites on the
metric system. Those that have been defined are:

Prefix   Symbol   Multiplier
yotta-     Y        10^+24
zetta-     Z        10^+21
exa-       E        10^+18
peta-      P        10^+15
tera-      T        10^+12
giga-      G        10^+9
mega-      M        10^+6
kilo-      k        10^+3
hecto-     h        10^+2
deca-      da       10^+1
deci-      d        10^-1
centi-     c        10^-2
milli-     m        10^-3
micro-     u        10^-6    (see note)
nano-      n        10^-9
pico-      p        10^-12
femto-     f        10^-15
atto-      a        10^-18
zepto-     z        10^-21
yocto-     y        10^-24

Note that the correct symbol for micro- (10^-6) is the lowercase Greek
letter mu, which looks sort of like a lowercase 'u' but with a tail on
the front. Since many symbol sets do not include the mu symbol, a
lowercase u is often substituted because if its similar look.

The big problem is not that larger prefixes have not been defined, but
that the meaning of those we have is ambiguous in the bits and bytes
world. Sometimes kB means 1000 bytes, as it should according to SI,
but usually it means 1024 bytes (2^10), a convenient measure when
working with binary numbers. Likewise, it isn't always clear whether
MB means 1,000,000, or 1024*1024, or even 1000*1024. This is a
problem. Here is an official source on one solution:

Prefixes for binary multiples (NIST)
http://physics.nist.gov/cuu/Units/binary.html

- Doctor Rick, The Math Forum
http://mathforum.org/dr.math/
```
Associated Topics:
High School Number Theory
Middle School Terms/Units of Measurement

Search the Dr. Math Library:

 Find items containing (put spaces between keywords):   Click only once for faster results: [ Choose "whole words" when searching for a word like age.] all keywords, in any order at least one, that exact phrase parts of words whole words

Submit your own question to Dr. Math
Math Forum Home || Math Library || Quick Reference || Math Forum Search