
Units of Measurement List 📐
All Units of Measurement List 📐 SI, Imperial & USC Units 🗒️
Units of measurement as defined by metrology, the scientific study of measurement. ADDucation’s units of measurement list in order 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.
- ADDucation’s list of all units of measurement was compiled by Joe Connor and last updated
Key: ≡ means “equivalent to” and ≈ means “approximately equal to” using a conversion factor. ADDucation Tips: Click arrows in column headings to sort measurement units. Reload page for original sort order. Resize your browser to full screen and/or zoom out to display as many columns as possible. Click the ➕ icon to reveal any hidden columns. Start typing in the Filter table box below to quickly find any imperial or metric units of measurement inside the table.
List of units | Unit of | Symbol | System | Formula / Definition of Units of Measurement / Trivia |
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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). |
Inch | Length | in or “ | Imperial / USCS | 1 inch = 2.54 cm or 25.4 mm. |
Link (Gunter’s link) |
Length | l., li. or lnk. | Imperial / USCS | 1 link = 0.01 chain = 0.04 rod = 0.66 foot = 0.22 yard = 7.92 inches ≡ 0.201168 meters. Gunter’s chain, designed by Edmund Gunter in 1620 in England, was a metal chain made up of 100 links. Each link is 66⁄100 of a US survey foot, or exactly 7.92 inches. The link was widely used in surveying in English speaking countries until the 20th century.
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Foot | Length | ft | Imperial / USCS | 12 inches (or 30.48 cm or 304.8 mm).
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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. |
Rod/Perch / Pole/Lug |
Length | Imperial / USCS | 1 rod is 16 1⁄2 US survey feet = 5.0292 m. To convert US feet to international feet multiply by 1.000002000004000008000016000032 | |
Chain | Length | Imperial / USCS | 1 chain = 66 feet (22 yards) = 20.1168 meters. 1 chain = 4 rods or 100 links. 10 chains = 1 furlong. 80 chains = 1 international/statute mile. The distance between the stups on a cricket pitch is still defined as one chain. |
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Furlong | Length | Imperial / USCS | 1 furlong is 1⁄8 of a mile. One furlong = 220 yards ≡ 201.1680 meters. Race lengths in furlongs are still used in many countries, most noteably horse racing. | |
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. 1 square mile is 640 acres. |
Nautical Mile | Length | sm | Imperial | exactly 1,852 meters (or about 6,076 feet). |
Astronomical Unit | Length | AE | Metric | 149,597,870,700 m (or 1.49598 x 1011 m). |
Light Year | Length | lj | Metric | 9.4607 x 1015 m (or 9.4607 Pm) |
Parsec | Length | pc | Metric | 3.0857 x 1016 m. |
Square meter | Area | sqm or m2 | Metric (derived) | 1 square meter = 10,000 cm2 = 1,000,000 mm2 |
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. |
Acre | Area | acre | Imperial / USCS | 1 acre 43560 sq ft = 4046.873 m2 and ≡ 0.405 hectare. There are 640 acres in 1 square mile. In Imperial units (before 1 Jan 1964 and USCS units a “perfect acre” is also a rectangular area of 43,560 square feet, bounded by sides 660 feet (a furlong) long and 66 feet wide, which is also equivalent to: 220 yards by 22 yards (a chain) or 40 rods by 4 rods. Therefore an acre is equivalent to 160 square rods or 10 square chains. |
Hectare | Area | ha | Metric | 1 ha = 100 ares which is 10,000 m2 and ≡ 2.47 acres. |
Square inch | Area | in2 | Imperial | 1 square inch = 6.4516 cm2 |
Square feet | Area | ft2 | Imperial | 1 square foot = 144 square inches (12″ x 12″) = 0.093 m2 |
Square yard | Area | yd2 | Imperial | 1 square yard = 9 square feet = 0.836 m2 |
Square mile | Area | sq mi or mi2 | Imperial / USCS | 1 square mile = 2.59 km2 or 27,878,400 ft2 |
Cubic meter | Volume (V) | m3 | Metric | 1m x 1m x 1m = m3 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 4 ºC). |
Milliliter | Volume (V) | ml | Metric | 1 cm3 ≡ 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 in3 | USCS | 1 Cubic Inch ≈16.387 ml. |
Cubic Foot | Volume (V) | cu ft or ft3 | USCS | 1 Cubic Foot = 1,728 cu in and ≈ 28.317. |
Cubic Yard | Volume (V) | cu yd or yd3 | USCS | 1 Cubic Yard = 27 cu ft and ≈ 764.555 or 0.7645m3 |
Acre-Foot | Volume (V) | acre ft | USCS | 1 Acr -Foot = 43560 cu ft and ≈ 1233.48m3 |
Teaspoon | Volume (V) | tsp | Imperial / USCS |
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Tablespoon | Volume (V) | tbsp | Imperial / USCS |
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Fluid Ounce | Volume (V) | fl oz or oz. fl | Imperial / USCS |
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Cup | Volume (V) | cup | Imperial / USCS |
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Gill | Volume (V) | gill | Imperial / USCS |
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Pint | Volume (V) | pt or p | Imperial / USCS |
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Quart | Volume (V) | qt | Imperial / USCS |
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Gallon | Volume (V) | gal | Imperial / USCS |
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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 Cs-133 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/s2 | Imperial | 1 g = 32.174 ft/s2 = 386.1 in/s2 = 22 mph/s. |
Gravity Metric | Acceleration of Gravity (g) | m/s2 | Metric | 1 g = 9.81 m/s2 = 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 |
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Ton | Mass | ton | Imperial / USCS |
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Tonne |
Mass | t | Metric | 1000 kg ≈ 2204.622 lb (aka a metric ton in the USA). |
Slug | Mass | slug | USCS | 1 slug = 1 lbf·s2/ft (A mass that accelerates by 1 ft/s2 when a force of one pound (lbf) is exerted on it). |
Density | Density (ρ) | kg/m3 | Metric | Density = mass divided by volume in kilogram per cubic meter (kg/m3). |
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:
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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/m²). Heavier silks are more durable, more opaque and appear more “wooly”. Here’s some examples:
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Newton | Force, Weight (F) | N | Metric (derived) | Named after Sir Isaac Newton. Kg and m/s2 |
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 m2 x s-2 | |
Joule | Work, Energy (E) | J | Metric (derived) | N x m = W x s = kg x m2 x s-2 |
Watt | Power, Radiant Flux (P) | w | Metric (derived) | J x s-1 = kg x m2 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 | The bar is a metric unit of pressure (but not an SI unit). 1 bar= 100,000 Pa (1 bar = 105 Pa which is slightly less than current average atmospheric pressure on Earth at sea level.
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Pounds per square inch | Pressure | psi or lbf/in2 | Imperial | Pound-force per square inch (lbf/in2). PSI is a measure of force per unit area. 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:
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Fahrenheit | Temperature (T) | °F | Imperial / USCS | A measure of temperature based on the Fahrenheit scale proposed by physicist Daniel Gabriel Fahrenheit in 1724. On the Farenheit scale water freezes at 32 °F and boils at 212 °F under standard conditions. A rough rule of thumb to convert Farenheit to Centigrade is to subtract 30 then divide by 2 (or multiply by 2 and add 30 to convert °C to °F). |
Candela | Luminous Intensity (l) | cd | Metric (SI base unit) |
One of 7 SI base units of measurement. |
Candela per square metre | Luminance (L) | cd/m2 | 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 m2 x (s3 x A)-1 |
Ohm | Electrical Resistance, Impedance (R) | Ω | Metric (derived) | W x A-1 = kg x m2 x (s3 x A2)-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 C-12.
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. |
See also: Fundamental Physical Constants…
Related ADDucation Lists:
- List of Commonly Used Abbreviations (acronyms)…
- Printable Periodic Table of Elements…
- Units of measurement chart in German: Maßeinheiten & Formeln
- Help improve ADDucation’s units of measurement list by adding your comments below…
I was asked what an “ILK” is in measurement – do you have a definition of that? The only thing I found was related to the measurement of a medicine in liquid for injections…
Hi John, the only meausurment related reference to ILK we can find is the Institut für Luft und Kältetechnik (ILK) using a 3D phase doppler particle analyzer for non-invasive measurement of velocity flow.
This list is missing many current and valid measurements, e.g. furlong, as well as almost all units marked as archaic, which are still legal use around the world e.g. rod, a measure of area. Another example is the dram, a unit of volume.
Thanks for your comment. We have now added furlong, chain, rod (which is a unit of length, not area) and link. We have not marked any units of measurement as archiac (meaning very old or old-fashioned) even though many are, whether they are legal or not. Dram was already in the list.