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Metric (SI) Prefixes
Metric Units of Measurement
In the metric system of measurement, designations of multiples and subdivision of any unit may be arrived at by combining with the name of the unit the prefixes deka, hecto, and kilo meaning, respectively, 10, 100, and 1000, and deci, centi, and milli, meaning, respectively, one-tenth, one-hundredth, and one-thousandth. In some of the following metric tables, some such multiple and subdivisions have not been included for the reason that these have little, if any currency in actual usage.
In certain cases, particularly in scientific usage, it becomes convenient to provide for multiples larger than 1000 and for subdivisions smaller than one-thousandth. Accordingly, the following prefixes have been introduced and these are now generally recognized.
| Prefixes | |||||
| Purpose | Prefix Name | Pronunciation | Prefix Symbol | Value | |
|---|---|---|---|---|---|
larger quantities or whole units |
yotta | yot'uh | Y | 1024 | Septillion |
| zetta | zet'uh | Z | 1021 | Sextillion | |
| exa | ex'a a as in about |
E | 1018 | Quintillion | |
| peta | as in petal | P | 1015 | Quadrillion | |
| tera | as in terrace | T | 1012 | Trillion | |
| giga | jig'a a as in about |
G | 109 | Billion | |
| mega | as in megaphone | M | 106 | Million | |
| kilo | as in kilowatt | k | 103 | Thousand | |
| hecto | heck'toe | h | 102 | Hundred | |
| deka | deck'a a as in about |
da | 101 | Ten | |
| 100 | One | ||||
| smaller quantities or sub units |
deci | as in decimal | d | 10-1 | Tenth |
| centi | as in sentiment | c | 10-2 | Hundredth | |
| milli | as in military | m | 10-3 | Thousandth | |
| micro | as in microphone | μ | 10-6 | Millionth | |
| nano | nan'oh an as in ant |
n | 10-9 | Billionth | |
| pico | peek'oh | p | 10-12 | Trillionth | |
| femto | fem'toe fem as in feminine |
f | 10-15 | Quadrillionth | |
| atto | as in anatomy | a | 10-18 | Quintillionth | |
| zepto | zep'toe | z | 10-21 | Sextillionth | |
| yocto | yok'toe | y | 10-24 | Septillionth | |
FAQ: How do I pronounce the prefix giga? The preferred pronunciation for the scientific term giga is jig'a (soft “g”). The hard "g" pronunciation of giga is frequently heard in common parlance. Some Prefix Etymology resources list both soft and hard “g” pronunciations. A great example where popular culture correctly portrays technical information is the classic movie scene from the film Back to the Future (1985) where characters Dr. Emmet Brown (Christopher Lloyd) and Marty McFly (Michael J. Fox) discuss “1.21 gigawatts” using the soft “g”. The SI helps the international scientific community communicate written technical information effectively and overcome the variations of language, including spelling and pronunciation. Verbal pronunciation of SI terminology is purposefully not addressed most SI style guides, which focus on written communication.
| Whole Units | Decimal Units | |||||
| thousands | hundreds | tens | basic unit | tenths | hundredths | thousandths |
|---|---|---|---|---|---|---|
| 1000 | 100 | 10 | 1 | 0.1 | 0.01 | 0.001 |
| kilo- | hecto- | deka- | meter gram liter |
deci- | centi- | milli |
| Units of Length | |
| 10 millimeters (mm) | 1 centimeter (cm) |
| 10 centimeters | 1 decimeter (dm) = 100 millimeters |
| 10 decimeters | 1 meter (m) = 1000 millimeters |
| 10 meters | 1 dekameter (dam) |
| 10 dekameters | 1 hectometer (hm) = 100 meters |
| 10 hectometers | 1 kilometer (km) = 1000 meters |
| Units of Area | |
| 100 square millimeter (mm2) | 1 square centimeter (cm2) |
| 100 square centimeter | 1 square decimeter (dm2) |
| 100 square decimeters | 1 square meter (m2) |
| 100 square meters | 1 square dekameter (dam2) = 1 are |
| 100 square dekameters | 1 square hectometer (hm2) = 1 hectare (ha) |
| 100 square hectometers | 1 square kilometer (km2) |
| Units of Liquid Volume | |
| 10 milliliters (mL) | 1 centiliter (cL) |
| 10 centiliters | 1 deciliter (dL) = 100 milliliters |
| 10 deciliters | 1 liter1 = 1000 milliliters |
| 10 liters | 1 dekaliter (daL) |
| 10 dekaliters | 1 hectoliter (hL) = 100 liters |
| 10 hectoliters | 1 kiloliter (kL) = 1000 liters |
| Units of Volume | |
| 1000 cubic millimeters (mm3) | 1 cubic centimeter (cm3) |
| 1000 cubic centimeters | 1 cubic decimeter (dm3) 1 000 000 cubic millimeters |
| 1000 cubic decimeters | 1 cubic meter (m3) 1 000 000 cubic centimeters 1 000 000 000 cubic millimeters |
| Units of Mass | |
| 10 milligrams (mg) | 1 centigram (cg) |
| 10 centigrams | 1 decigram (dg) = 100 milligrams |
| 10 decigrams | 1 gram (g) = 1000 milligrams |
| 10 grams | 1 dekagram (dag) |
| 10 dekagrams | 1 hectogram (hg) = 100 grams |
| 10 hectograms | 1 kilogram (kg) = 1000 grams |
| 1000 kilograms | 1 megagram (Mg) or 1 metric ton(t) |
Contacts
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Metric Program