# Powers of Ten – Metric Prefixes

Prefixes can be used to express the ‘x’ in this number. This table will show you which metric prefix to use for different values of ‘x’. Credit: Todd Helmenstine

Scientific notation is a useful means to write out very large or very small numbers. Spelling out scientific notation numbers can be a mouthful. The number 5 x 106 could be said “five times ten to the six”, but it is easier to say “five million”. We have words that express the very large and the very small.

The same is true for the metric system or SI units. These measurements are based on powers of ten, just like scientific notation. Every three powers of ten has its own metric prefix. There are a couple of special powers of ten that have their own prefix outside the ‘every three’ pattern.

The wavelength of microwaves are on the order of 10-6 meters. The prefix for 10-6 is micro, so you can say the wavelength of a microwave is on the order of one micrometer. (This also makes it obvious why they’re called microwaves.) The symbol for micro is the Greek letter μ. 1 micrometer is written as 1 μm.

The distance between the Earth and the Moon is about 384,000,000 meters. The Mega prefix (symbol M) means one million, so you could say the distance is 384 Megameters or 384 Mm.

Substituting the metric prefix can make doing calculations easier in your head. Use the prefix that applies to your situation. This table of metric prefixes has the standard names for each prefix used in science and measurements. It also shows the symbol used to represent these prefixes, their ‘power of ten’ and the number you are actually replacing with the prefix.

 Prefix Symbol x from 10x Number yotta Y 24 1,000,000,000,000,000,000,000,000 zetta Z 21 1,000,000,000,000,000,000,000 exa E 18 1,000,000,000,000,000,000 peta P 15 1,000,000,000,000,000 tera T 12 1,000,000,000,000 giga G 9 1,000,000,000 mega M 6 1,000,000 kilo k 3 1,000 hecto h 2 100 deca da 1 10 base 0 1 deci d -1 0.1 centi c -2 0.01 milli m -3 0.001 micro μ -6 0.000001 nano n -9 0.000000001 pico p -12 0.000000000001 femto f -15 0.000000000000001 atto a -18 0.000000000000000001 zepto z -21 0.000000000000000000001 yocto y -24 0.000000000000000000000001

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