Numbers smaller than 1

(fractions)

Deci is a tenth    

Decimal, decade. The decimeter is rarely used, but it means one 10th of a meter. People usually say 10 centimeters instead.

.1    10-1

Centi is a hundredth   

Century, cent and centennial

One centimeter is about the width of the fingernail on your pinky finger.

.01    10-2

Milli is a thousandth

Millisecond, millimeter

.001    10-3

Micro is a millionth

A micrometer (a micron or µm) is a millionth of a meter.  Bacteria, human cells are at this scale.

.000001    10-6

Nano is a billionth 

A nanometer is a billionth of a meter. The realm of molecules.

.000000001   10-9

Pico is a trillionth

A picoliter is a trillionth of a liter. A hydrogen atom is about 50 picometers across.

10-12

Femto is a quadrillionth 

The fastest chemical reactions in living cells take place in about 200 femtoseconds.

10-15

Atto is a quintillionth

New stories about atomic physics sometimes refer to events that occur in attosseconds.

10-18

Zepto is a sextillionth                  

10-21

Yocto =  10-24

Yoctometers are used to describe dimensions of sub-atomic particles.

Planck Length = 10-35 

Regarded as the smallest unit that makes any sense in physical reality. The diameter of a proton is about 1020 Planck lengths.

Understanding the prefixes that come with large and small numbers helps make the value of numbers clearer, when we encounter them in the news.

The leaps of scale represented by these prefix names are huge.

One nanosecond, for instance, seems like a very short span, and it is. A billion of them went by just in the last second.  But each nanosecond that passes contains a million femtoseconds.

Tiny news items

Extremely tiny items are almost always reported in units that are specific fractions of a meter. A micron (micrometer) is a millionth of a meter, and a nanometer is a billionth of a meter.  Things measured in these units are extremely small. There are 25,400,000 nanometers in a single inch. And things get much smaller after that. Small units of time, like nanoseconds, are specific fractions of a second.

Numbers bigger than 1

(counting things)

Kilo is a thousand

Kilogram. Kilowatt.

Mega is a million

One megavolt is one million volts.

Giga is a billion

A gigawatt is a billion watts.

Tera is a trillion

A terabyte is a trillion bytes.

Peta is a quadrillion 

A petaflop is the computing speed required to perform a quadrillion mathematical operations in one second.

Exa is a quintillion

Exabyte.

Number prefixes

Prefix converter