Metric and SI Unit Abbreviations
64 abbreviations · part of Units of Measurement Abbreviations
Symbols of the International System of Units (SI) and the wider metric system: base units, derived units such as the newton and tesla, the 24 decimal prefixes from quecto- to quetta-, and everyday metric units of length, mass, volume and area. SI symbols are case-sensitive, take no period and are never pluralized, so 5 kg is correct and 5 Kgs is not. The system is maintained by the International Bureau of Weights and Measures (BIPM), and since 20 May 2019 every base unit has been defined by a fixed constant of nature.
| Abbreviation | Stands for | Description |
|---|---|---|
| a | Atto- (quintillionth) | Attosecond light pulses that capture the motion of electrons are the main use of atto-, which denotes 10^-18. |
| amu | Atomic mass unit | A unit of mass for atoms and molecules equal to one twelfth of the mass of a carbon-12 atom, about 1.6605 × 10^-27 kg. |
| AU | Astronomical unit | Unit of distance roughly equal to the average distance between Earth and the Sun, fixed by the International Astronomical Union in 2012 at exactly 149,597,870,700… |
| Bq | Becquerel | Radioactivity equal to one nuclear decay per second. |
| c | Centi- (hundredth) | One hundredth (10^-2) of a unit. |
| CBM | Cubic meter (freight) | Shipping and logistics abbreviation for cubic meter, the unit used to quote less-than-container-load (LCL) ocean freight and container capacity. |
| cc | Cubic centimeter | One cubic centimeter, exactly equal to one milliliter. |
| cd | Candela | The SI base unit of luminous intensity, measuring how bright a light source appears to the human eye in a particular direction. |
| CGS | Centimeter-gram-second system | An older metric system built on the centimeter, gram and second, standard in physics before SI. |
| cL | Centiliter | One hundredth of a liter, 10 mL, widely used on European bottle labels, drinks menus and cocktail recipes. |
| cm | Centimeter | One hundredth of a meter, about 0.394 inch, used for body height, clothing sizes, rulers, snowfall and small objects. |
| ct | Carat | A unit of mass for gemstones and pearls equal to exactly 200 milligrams, so a 1 ct diamond weighs 0.2 g. |
| d | Deci- (tenth) | One tenth (10^-1) of the base unit. |
| Da | Dalton | A unit of molecular mass equal to the unified atomic mass unit, one twelfth the mass of a carbon-12 atom. |
| dL | Deciliter | One tenth of a liter, 100 mL. |
| dm | Decimeter | Ten centimeters, one tenth of a meter. |
| E | Exa- (quintillion) | A factor of 10^18, a million trillion. |
| eV | Electronvolt | Energy gained by an electron accelerated through a potential difference of one volt, about 1.602 × 10^-19 joule. |
| F | Farad | Capacitance at which one coulomb of charge raises a capacitor's voltage by one volt. |
| g | Gram | One thousandth of a kilogram, about 0.035 ounce. |
| gsm | Grams per square meter | Weight of paper, card, fabric or towels expressed as mass per unit area, written g/m² in formal specifications. |
| Gt | Gigatonne | One billion tonnes, the headline unit for global carbon emissions, carbon budgets and ice-sheet loss. |
| Gy | Gray | Absorbed radiation dose, one joule of energy deposited per kilogram of tissue or material. |
| h | Hecto- (hundred) | One hundred times the base unit (10^2). |
| ha | Hectare | A metric unit of land area equal to 10,000 square meters, a square 100 m on a side, or about 2.471 acres. |
| hL | Hectoliter | One hundred liters, the standard unit for production and trade statistics in the wine, beer and dairy industries. |
| k | Kilo- (thousand) | The thousand multiplier, 10^3, and the most widely used metric prefix in daily life: kilometer, kilogram, kilowatt and kilobyte. |
| kat | Katal | Catalytic activity of an enzyme or catalyst that converts one mole of substrate per second. |
| kg | Kilogram | The SI base unit of mass, about 2.2046 pounds. |
| km | Kilometer | One thousand meters, about 0.621 mile, the standard unit for road distances, speed limits and running races in metric countries. |
| km² | Square kilometer | Area of a square 1 km on a side, equal to 100 hectares or about 0.386 square mile. |
| kN | Kilonewton | One thousand newtons, roughly the weight of a 102 kg mass on Earth. |
| kt | Kiloton (TNT equivalent) | Explosive energy equal to one thousand tons of TNT, about 4.184 terajoules, the standard measure of nuclear weapon yields below the megaton range. |
| L | Liter | A metric unit of volume equal to one cubic decimeter (1,000 cm³), or about 1.057 US quarts. |
| ly | Light-year | Distance light travels in a vacuum in one Julian year, about 9.46 trillion kilometers (5.88 trillion miles). |
| m | Meter | The SI base unit of length, defined since 1983 as the distance light travels in a vacuum in 1/299,792,458 of a second. |
| mcg | Microgram | One millionth of a gram, used for potent drugs, hormones and vitamins such as vitamin B12, vitamin D and folate. |
| mg | Milligram | The standard unit for tablet strengths, vitamin content and sodium on nutrition labels, equal to a thousandth of a gram. |
| MKS | Meter-kilogram-second system | The metric system based on the meter, kilogram and second that preceded and evolved into SI. |
| mL | Milliliter | A thousandth of a liter, identical to one cubic centimeter. |
| mm | Millimeter | A thousandth of a meter, about 0.039 inch, used for precise dimensions in engineering drawings, rainfall totals, camera lenses, fasteners, jewelry and screen sizes in… |
| mmol | Millimole | A thousandth of a mole, the unit used outside the US for blood glucose (mmol/L), cholesterol, electrolytes and many other lab results. |
| mol | Mole | The SI base unit for amount of substance, defined since 2019 as exactly 6.02214076 × 10^23 elementary entities, the Avogadro number. |
| mSv | Millisievert | Practical unit for medical imaging and background radiation doses. |
| Mt | Megaton (TNT equivalent) | A measure of explosive energy equal to one million tons of TNT, about 4.184 petajoules, used for thermonuclear weapons and large asteroid impacts. |
| m² | Square meter | The SI unit of area, a square one meter on each side, about 10.76 square feet. |
| m³ | Cubic meter | SI unit of volume, a cube 1 m on each side, holding 1,000 liters or about 264 US gallons. |
| N | Newton | Force that accelerates a 1 kg mass at 1 meter per second squared, the SI unit for push, pull and weight. |
| ng | Nanogram | A billionth of a gram, used in laboratory measurements of hormones, drugs, tumor markers and toxins. |
| nm | Nanometer | One billionth of a meter, the scale of molecules, light wavelengths and transistor features. |
| P | Peta- (quadrillion) | Peta- multiplies by 10^15, a thousand trillion. |
| pc | Parsec | Astronomical unit of distance equal to about 3.26 light-years or 206,265 astronomical units. |
| q | Quecto- (10^-30) | The smallest SI prefix, 10^-30, adopted in 2022. |
| R | Ronna- (10^27) | Adopted in November 2022 at the 27th General Conference on Weights and Measures, ronna- denotes 10^27. |
| rad | Radian | The SI unit of plane angle: the angle at the center of a circle subtended by an arc equal in length to the radius. |
| S | Siemens | Electrical conductance, the reciprocal of resistance: a conductor of 1 ohm has a conductance of 1 S. |
| SI | International System of Units | The modern metric system, used officially by nearly every country and universally in science, medicine and international trade. |
| sr | Steradian | The SI unit of solid angle, the three-dimensional counterpart of the radian. |
| Sv | Sievert | Equivalent and effective radiation dose, which adjusts absorbed energy for the type of radiation and the sensitivity of each organ to estimate health risk. |
| T | Tera- (trillion) | Trillion-fold multiplier (10^12) used in terabyte, terawatt-hour and terahertz. |
| um | Micrometer (micron) | One millionth of a meter, properly written μm with the Greek letter mu; um is the plain-text substitute used where that character is unavailable. |
| Wb | Weber | The SI unit of magnetic flux, equal to one volt-second. |
| y | Yocto- (septillionth) | Until 2022 the smallest SI prefix, yocto- denotes 10^-24. |
| Z | Zetta- (sextillion) | Zetta- denotes 10^21 and is used for zettabytes of data created worldwide and for zettajoules of heat absorbed by the oceans in climate research. |
More units of measurement abbreviations
- Cooking Abbreviations (43)
- Data Unit Abbreviations (36)
- Day of the Week Abbreviations (22)
- Engineering Unit Abbreviations (103)
- Math Abbreviations (91)
- Month Abbreviations (12)
- Statistics Abbreviations (88)
- Time Abbreviations (51)
- Time Zone Abbreviations (64)
- US Customary and Imperial Unit Abbreviations (43)