Units of Measurement
Units of Measurement – List of SI, Imperial & US Customary Units
Units of measurement list including Metric SI units (International System of Units), Imperial units and Unites States Customary Units (USCS). Where British, American, Canadian and Australian imperial units of volume differ we’ve included the differences.
Base SI Units of Measurement Dependencies Notes
 Metre is dependent on second because its length is defined in terms of the distance traveled by light in a fraction of a second.
 Candela and Ampere both depend on the definition of energy which is defined in terms of length (metre), mass (kilogram) and time (second).
 Mole is dependent on kilogram because it is defined in terms of the weight of carbon atoms.
Key: ≡ means “equivalent to” and ≈ means “approximately equal to” using a conversion factor.
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Measurement  Unit of  Symbol  System  Formula / Definition of Units of Measurement 

Meter/Metre  Length  m  Metric (SI base unit)  Since 1983 a meter is defined as the distance light travels in a vacuum in 1,299,792,458th of a second. 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  1,49598 x 10^{11 }m 
Light Year  Length  lj  Metric  9,4505 x 10^{15 }m 
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  Imperial / USCS  1,760 yards or 5,280 feet (or 1609 m or 1.61 km) 
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 inches  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 yards  Area  yd^{2}  Imperial  1 square yard = 9 square feet = 0.836 m^{2} 
Square miles  Area  mi^{2}  Imperial  1 square mile = 2.59 km^{2} 
Cubic meter  Volume (V)  m^{3}  Metric  1m x 1m x 1m 
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 the standard 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 secound. 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 
Kilogram  Mass  kg  Metric (SI base unit)  1 kilogram = 1000g and is the mass of an international kilogram prototype (a cylinder made from a platinumiridium alloy) ≈ 2.2 pounds. One of 7 SI base units of measurement 
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}) 
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  Deprecated  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 Kelvin is the 1/273.15 of the thermodynamic temperature of the triple point of water = 0.01°C. One of the 7 Metric 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 Candela = the light from one candle. Today the color of the light and its direction also have to be taken into account. Based on a frequency of 540 x 10^{12} cycles per second in Hertz the color is yellowish green, which the human eye distinguishes really well. 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)  Used to express the flow rate of electric charge. 1 ampere equates to a flow of one coulomb per second. 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, Impedence (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. It’s called the Avogadro constant and is approximately 6.022169 x 10^{23}. 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 
More ADDucation Lists Related to Units of Measurement:
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 PS: German speakers can find more units of measurement on Maßeinheiten & Formeln
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