Units of Measurement Lists
Units of Measurement – List of SI, Imperial & USC Units
Units of measurement as defined by metrology, the scientific study of measurement. ADDucation’s units of measurement list includes Metric SI units (International System of Units), Imperial units and United States Customary System (USCS). Where British, American, Canadian and Australian imperial units of volume differ we’ve included the differences.
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Measurement  Unit of  Symbol  System  Formula / Definition of Units of Measurement / Trivia 

Meter/Metre  Length  m  Metric (SI base unit) 
One of 7 SI base units of measurement. 
Millimeter  Length  mm  Metric  0.001 m (1/1000th of a meter). 
Centimeter  Length  cm  Metric  0.01 m (1/100th of a meter). 
Decimeter  Length  dm  Metric  0.1 m (1/10th of a meter). 
Kilometer  Length  km  Metric  1000 meters (or 0.62137 mile or 3,280.8 feet). 
Astronomical Unit  Length  AE  Metric  149,597,870,700 m (or 1.49598 x 10^{11 }m). 
Light Year  Length  lj  Metric  9.4607 x 10^{15 }m (or 9.4607 Pm) 
Parsec  Length  pc  Metric  3.0857 x 10^{16} m. 
Inch  Length  in or “  Imperial / USCS  1 inch = 2.54 cm or 25.4 mm. 
Foot  Length  ft  Imperial / USCS  12 inches (or 30.48 cm or 304.8 mm). 
Yard  Length  yd  Imperial / USCS  3 feet or 36 inches (or 91.44 cm or 914.4 mm). The international yard is defined as exactly 0.9144 metres so it is effectively one of the fundamental Imperial units of measurement. 
Mile  Length  mi or m or ml  Imperial / USCS  1,760 yards or 5,280 feet. In 1959, by international agreement, one mile was standardized as exactly 1,609.344 metres. 
Nautical Mile  Length  sm  Imperial  exactly 1,852 meters (or about 6,076 feet). 
Square meter  Area  sqm or m^{2}  Metric (derived)  1 square meter = 10,000 cm^{2} = 1,000,000 mm^{2} 
Acre  Area  acre  Imperial / USCS  1 acre 43560 sq ft = 4046.873 m^{2} and ≡ 0.405 hectare. 
Are  Area  a or ares  Metric (derived)  1 are = 100 m² ≡ 0.0247 acre. 100 ares = 1 hectare, the most common unit of land measurement in the world. 
Hectare  Area  ha  Metric  1 ha = 100 ares which is 10,000 m^{2} and ≡ 2.47 acres. 
Square inch  Area  in^{2}  Imperial  1 square inch = 6.4516 cm^{2} 
Square feet  Area  ft^{2}  Imperial  1 square foot = 144 square inches (12″ x 12″) = 0.093 m^{2} 
Square yard  Area  yd^{2}  Imperial  1 square yard = 9 square feet = 0.836 m^{2} 
Square mile  Area  sq mi or mi^{2}  Imperial / USCS  1 square mile = 2.59 km^{2} or 27,878,400 ft^{2} 
Cubic meter  Volume (V)  m^{3}  Metric  1m x 1m x 1m = m^{3 }The original metric system included stere (stère) as a unit of volume for firewood. 
Liter  Volume (V)  l  Metric  (rough guide: 1 liter of water weighs approximately 1kg at 4ºC). 
Milliliter  Volume (V)  ml  Metric  1 cm^{3} ≡ 0,001 liter. 
Centiliter  Volume (V)  cl  Metric  0,01 l ≡ 10 ml. 
Deciliter  Volume (V)  dl  Metric  0,1 l ≡ 100 ml. 
Hectoliter  Volume (V)  hl  Metric  100 liters. 
Cubic Inch  Volume (V)  cu in or in^{3}  USCS  1 Cubic Inch ≈16.387 ml. 
Cubic Foot  Volume (V)  cu ft or ft^{3}  USCS  1 Cubic Foot = 1,728 cu in and ≈ 28.317. 
Cubic Yard  Volume (V)  cu yd or yd^{3}  USCS  1 Cubic Yard = 27 cu ft and ≈ 764.555 or 0.7645m^{3} 
AcreFoot  Volume (V)  acre ft  USCS  I Acr Foot = 43560 cu ft and ≈ 1233.48m^{3} 
Teaspoon  Volume (V)  tsp  Imperial / USCS 

Tablespoon  Volume (V)  tbsp  Imperial / USCS 

Fluid ounce  Volume (V)  fl oz or oz. fl  Imperial / USCS 

Cup  Volume (V)  cup  Imperial / USCS 

Gill  Volume (V)  gill  Imperial / USCS 

Pint  Volume (V)  pt or p  Imperial / USCS 

Quart  Volume (V)  qt  Imperial / USCS 

Gallon  Volume (V)  gal  Imperial / USCS 

Radian  Angle (α)  rad or ^{c}  Metric (derived)  1 rad = 57.295° (2Π radians = 360 degrees, which is a circle). 
Degree  Angle (α)  ° or deg  Metric  Π/180° = 0.01745329 rad (1 degree = Π/180 radians). 
Steradian  Solid angle (Ω)  sr  Metric (derived)  A steradian is (180/Π)^{2} square degrees (about 3282.8 square degrees). 
Second  Time (t)  s  Metric (SI base unit)  1 second = 9,192,631,770 cycles of radiation of an atom of Cs133 transition (the period required by electrons flitting between 2 energy levels in a Caesium isotope). One of 7 SI base units of measurement. 
Minute  Time (t)  min  Metric (derived)  60 seconds. 
Hour  Time (t)  h  Metric (derived)  60 min ≡ 3,600 seconds. 
Day  Time (t)  d  Metric (derived)  24 hours ≡ 1,440 minutes or 86,400 seconds. 
Year  Time (t)  a  Metric (derived)  365.24 days. 
Hertz  Frequency (f)  Hz  Metric (derived)  One cycle per second: 1/s or s^{−1} 
Angular Frequency  Frequency (f)  ω  Metric  Radians per second. 1 x s^{1} ≡ 60 x min^{1} 
Decibel  Sound  dB  Metric  Logarithmic unit to describe a ratio which could be intensity, power, sound pressure, voltage or in common usage loudness. 
Kilogram meters per second  Momentum  kg m/s  Metric  Momentum = Mass x Velocity. The derived unit is newton second. 
Miles per hour  Speed  mph  Imperial  Distance divided by time. 
Meters per second  Speed  m/s or kph  Metric  Distance divided by time. 
Gravity Imperial 
Acceleration of Gravity (g)  ft/s^{2}  Imperial  1 g = 32.174 ft/s^{2 }= 386.1 in/s^{2 }= 22 mph/s.^{} 
Gravity Metric  Acceleration of Gravity (g)  m/s^{2}  Metric  1 g = 9.81 m/s^{2} = 35.30394 (km/h)/s. 
Feet per second  Mass  ft/s  Imperial  
Grams  Mass  g  Metric (derived)  1000 grams = 1 kg or 1 gram = 0.001 kg. The original metric system included “gramme” as the unit of mass for 1 cubic centimeter of water but was quickly deemed too small. The “kilo” prefix was added resulting in “kilogramme”. 
Kilogram 
Mass  kg  Metric (SI base unit) 
One of 7 SI base units of measurement. The kilogram is the only SI base unit with an SI prefix (see Grams). 
Grain  Mass  gr  Imperial / USCS  1 Grain = 1⁄7000 lb and ≈ 0.0648 g or 64.8 mg. 
Dram  Mass  dr  Imperial / USCS  1 Dram = 27 11⁄32 gr and ≈ 1.77 g. 
Ounce  Mass  oz  Imperial  1 Ounce = 1/16 pound or 16 dr ≈ 28.35 g. 
Pound  Mass  lb  Imperial / USCS  1 Pound = 16 oz ≈ 0.45 kg. The pound is one of the fundamental Imperial units of measurement. 
Hundredweight  Mass  cwt  Imperial / USCS 

Ton  Mass  ton  Imperial / USCS 

Tonne 
Mass  t  Metric  1000 kg ≈ 2204.622 lb (aka a metric ton in the USA). 
Slug  Mass  slug  USCS  1 slug = 1 lb_{f}·s^{2}/ft (A mass that accelerates by 1 ft/s^{2} when a force of one pound (lb_{f}) is exerted on it). 
Density  Density (ρ)  kg/m^{3}  Metric  Density = mass divided by volume in kilogram per cubic meter (kg/m^{3}). 
Denier  Linear Density  den or D  Metric (derived)  Linear density is a measure of the fineness or heaviness of yarn/fiber/fibre used in textiles. Denier is most common used in 🇬🇧UK and US. 1 denier = 1/9,000,000 kg/m = 1.111 111^{7} kg/m. 1 denier = 0.035 ounces/5.6 miles of yarn/fiber/fibre. For example, denier is still commonly used to describe the thickness/opacity of tights and pantyhose:

Tex  Linear Density  tex  Metric (derived)  Linear density is a measure of the “fineness” of yarn/fiber/fibre used in textiles. Tex is most commonly used in 🇨🇦Canada and 🇪🇺Continental Europe. 1 tex = 1 gram per kilometer (1g/km) = 0.035 ounces/0.62 miles (0.35oz/0.62m) of yarn/fibre/fiber. 
Decitex  Linear Density  dtex  Metric (derived)  Linear density is a measure of the “fineness” of yarn/fiber/fibre used in textiles. Decitex is the SI unit for the linear density of fibers/fibres/yarn in kg/m. 1 dtex = 0.0000001 kg/m ≡ 1 gram per 10 kilometers. 
Mommes  Weight  mm  Traditional  Mommes is the traditionally used to measure the weight of silk fabrics. Mommes is just one of many specialized unit of measurements still used in the textile industry. 1 momme = 0.1280019 ounces per square yard (4.340 g/m^{²}). Heavier silks are more durable, more opaque and appear more “wooly”. Here’s some examples:

Newton  Force, Weight (F)  N  Metric (derived)  Named after Sir Isaac Newton. Kg and m/s^{2} 
Kilopond  Force (F)  kp  Metric  9.80665 Newtons 
Pond  Force (F)  p  Metric  9,80665 x 10^{3} Newtons 
Newton meter  Torque (M)  Metric  N x m = kg x m^{2} x s^{2}  
Joule  Work, Energy (E)  J  Metric (derived)  N x m = W x s = kg x m^{2} x s^{2} 
Watt  Power, Radiant Flux (P)  w  Metric (derived)  J x s^{1} = kg x m^{2} x s^{3} 
Kilowatt  Power (P)  kw  Metric  1 Kilowatt ≡ 1,000 Watts. 
Horsepower  Power (P)  hp  Traditional  1 horsepower equates to the power required to lift 75 kg 1 meter in 1 second which is 735.5w. Horsepower is officially obsolete but still in common usage. 
Pascal  Pressure, Stress  Pa  Metric (derived)  One newton per square metre. Named after Blaise Pascal. 
Bar  Power (P)  bar  Metric  1 bar ≡ 10^{5} Pa 
Pounds per square inch  Pressure  psi or lbf/in^{2}  Imperial  1 psi ≈ 6894.8 Pascal or 0.0689 Bar. 
Kelvin  Temperature (T)  K  Metric (SI) 
One of 7 SI base units of measurement. 
Centigrade  Temperature (T)  °C  Metric (derived)  0°C is the freezing point of water. Absolute zero is 273.15°C or 0 Kelvin. 
Calorie  Amount of Heat (Q)  Cal or kcal / cal  Metric  1 Thermochemical calorie = 4.1868 Joules. There are two common uses:

Fahrenheit  Temperature (T)  °F  Imperial / USCS  Temperature scale on which water freezes at 32°F and boils at 212°F under standard conditions. 
Candela  Luminous Intensity (l)  cd  Metric (SI base unit) 
One of 7 SI base units of measurement. 
Candela per square metre  Luminance (L)  cd/m^{2}  Metric (derived)  The intensity of light emitted from a surface per unit area in a given direction. 
Lumen  Luminous Flux (Φ)  lm  Metric (derived)  cd x sr. A lumen is the measure of the total amount of visible light emitted from a source, taking into account the beam and angle. 
Lux  Illuminance (E)  lx  Metric (derived)  One lumen per square metre. lm x s = cd x sr x m^{2} 
Lumen Seconds  Light quantity (Q)  ls  Metric  lm x s 
Diopter  Refractive Index (D)  dpt  Metric  1 x m^{1} 
Ampere  Current (I)  A / Amps  Metric (SI base unit)  Ampere is used to express the flow rate of electric charge.
One of 7 SI base units of measurement. 
Coulomb  Electric Charge (Q)  C  Metric (derived)  Charge carried by a constant current of one ampere in one second. 
Volt  Voltage, Electrical (U)  V  Metric (derived)  Potential difference in charge expressed as a ratio between two points in an electrical field. W x A^{1} = kg x m^{2} x (s^{3} x A)^{1} 
Ohm  Electrical Resistance, Impedance (R)  Ω  Metric (derived)  W x A^{1} = kg x m^{2} x (s^{3} x A^{2})^{1 } (Mnemonic to remember the order of color coding on resistors)^{} 
Farad  Electrical Capacitance (F)  F  Metric (derived)  One farad is the capacitance across which, when charged with one coulomb, has a potential difference of one volt. Named after Michael Faraday. 
Siemens  Electrical Conductance (S)  S  Metric (derived)  One Siemens is equal to the reciprocal of one ohm. Named after Ernst Werner von Siemens. 
Henry  Electrical Inductance (H)  H  Metric (derived)  The inductance of a closed circuit in which an electromotive force of one volt is produced when the electric current in the circuit varies uniformly at a rate of one ampere per second. Named after Joseph Henry. 
Weber  Magnetic Flux (Wb)  Wb  Metric (derived)  A change in flux of one Weber per second induces an electromotive force of one volt. Named after Wilhelm Eduard Weber. 
Tesla  Magnetic Flux Density, Magnetic Field (T)  (T)  Metric (derived)  One tesla is equal to one Weber per square metre. Named after Nikola Tesla. 
Becquerel  Radioactive Decay  Bq  Metric (derived)  Bq = 1 x s^{1} 
Mole  Amount of Substance (s)  mol  Metric (SI base unit)  One mole is the number of atoms in 12 thousandths of a kilogram of carbon C12.
One of 7 SI base units of measurement. 
Paper Bale  Paper Quantity  ream  Imperial  1 ream = 500 sheets of paper. 
Dozen  Quantities  dz or doz  Imperial  12 items, eggs are commonly sold as half a dozen or a dozen. A bakers dozen is 13 items, 12+1 to be sure they were not underweight. 
Related ADDucation Lists:
 List of Commonly Used Abbreviations (acronyms)…
 Printable Periodic Table of Elements…
 Units of measurement in German: Maßeinheiten & Formeln
 ADDucation’s units of measurement list was compiled by Joe Connor, last updated 25 Mar 2020.
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