Units Encyclopedia
Definitions, history and use cases for all 114+ units of measurement. Each unit page links directly to all conversions involving it.
Length
Category page →Meterm
The meter is the base SI unit of length, defined since 1983 by the speed of li…
Kilometerkm
The kilometer is the international standard for road distances and travel, use…
Centimetercm
The centimeter is the everyday metric unit for body measurements, clothing siz…
Millimetermm
The millimeter is the precision unit used in engineering, manufacturing, and w…
Milemi
The statute mile is the official road-distance unit in the United States, the …
Yardyd
The yard is the standard length unit in American football, British cricket, an…
Footft
The foot is the standard unit for human height, building floor counts, and avi…
Inchin
The inch is the global standard for screen sizes, pipe diameters, and shoe siz…
Nautical Milenmi
The nautical mile is the international navigation unit for marine and aviation…
Micrometerµm
The micrometer measures particle size, air quality (PM2.5), and microscopic bi…
Nanometernm
The nanometer is used in semiconductor manufacturing, fiber optics, and visibl…
Light Yearly
The light-year is the standard astronomical distance unit, equal to 9.461 tril…
Furlongfur
The furlong is a traditional eighth-of-a-mile unit, still used in horse racing…
Fathomftm
The fathom is the traditional marine depth unit, equal to six feet, used in na…
AngstromÅ
The angstrom is the historical unit for atomic and molecular dimensions, equal…
Weight
Category page →Kilogramkg
The kilogram is the base SI unit of mass and the global standard for body weig…
Gramg
The gram is the everyday metric unit for cooking ingredients, postage, and sma…
Milligrammg
The milligram is the standard unit for pharmaceutical dosing, vitamin labeling…
Microgramµg
The microgram is used in pharmacology, environmental science, and trace-elemen…
Poundlb
The pound is the everyday weight unit in the United States and the United King…
Ounceoz
The ounce is the standard small-weight unit in American kitchens, postage, and…
Metric Tont
The metric ton equals 1,000 kilograms and is the international standard for sh…
US Tonton (US)
The US short ton equals 2,000 pounds and is the standard unit for American fre…
UK Tonton (UK)
The UK long ton equals 2,240 pounds and remains in British shipping, mining, a…
Stonest
The stone equals 14 pounds and is the traditional British unit for personal bo…
Caratct
The carat equals 200 milligrams exactly and is the universal unit for gemstone…
Graingr
The grain is the smallest traditional weight unit, used in pharmaceutical comp…
Volume
Category page →LiterL
The liter is the everyday metric unit for beverages, fuel, and household liqui…
Milliliterml
The milliliter is the standard small-volume unit for cooking, pharmaceuticals,…
Cubic Meterm³
The cubic meter is the SI volume unit for water utilities, shipping containers…
US Gallongal (US)
The US gallon is the standard unit for fuel, milk, and beverages across the Un…
UK Gallongal (UK)
The UK imperial gallon is 20% larger than the US gallon and remains in British…
Fluid Ouncefl oz
The US fluid ounce is the standard unit for beverage portions, cocktail recipe…
Cupcup
The US cup equals 240 milliliters and is the cornerstone of American recipe me…
Pintpt
The pint is the standard pub-beer unit in the United Kingdom and a common meas…
Quartqt
The US quart equals one quarter of a gallon and is common for milk, motor oil,…
Tablespoontbsp
The tablespoon is the standard mid-size cooking measure, equal to 15 millilite…
Teaspoontsp
The teaspoon is the smallest standard cooking spoon, equal to 5 milliliters an…
Barrelbbl
The oil barrel equals 42 US gallons and is the global benchmark for crude oil …
Cubic Inchin³
The cubic inch measures classic American engine displacement and small-volume …
Cubic Footft³
The cubic foot is the American standard for HVAC capacity, natural gas billing…
Cubic Yardyd³
The cubic yard is the standard volume unit for American concrete delivery, mul…
Temperature
Category page →Celsius°C
Celsius is the global temperature standard for weather, science, and daily lif…
Fahrenheit°F
Fahrenheit is the everyday temperature scale in the United States, used for we…
KelvinK
The Kelvin is the SI thermodynamic temperature scale, starting at absolute zer…
Rankine°R
The Rankine scale is the absolute version of Fahrenheit, used in American engi…
Area
Category page →Square Meterm²
The square meter is the standard metric area unit for room sizes, real estate,…
Square Kilometerkm²
The square kilometer measures cities, national parks, and large geographic reg…
Square Centimetercm²
The square centimeter is used in engineering tolerances, biology specimen meas…
Square Millimetermm²
The square millimeter is the precision area unit for electronics, microfabrica…
Hectareha
The hectare equals 10,000 square meters and is the international standard for …
Acreac
The acre is the standard unit for American and British farmland, real estate, …
Square Footft²
The square foot is the standard unit for American and British residential and …
Square Inchin²
The square inch measures American printer paper coverage, manufacturing tolera…
Square Yardyd²
The square yard measures American carpet, fabric, and small landscaping projec…
Square Milemi²
The square mile measures American counties, large parks, and geographic region…
Rairai
The rai is the traditional Thai land unit, equal to 1,600 square meters, used …
Dunamdunam
The dunam is the historical Middle Eastern land unit, equal to 1,000 square me…
Time
Category page →Seconds
The second is the base SI unit of time, defined by the cesium-133 atomic trans…
Millisecondms
The millisecond is the standard unit for web latency, computer benchmarks, and…
Minutemin
The minute equals 60 seconds and is the universal unit for short durations in …
Hourh
The hour equals 3,600 seconds and structures workdays, broadcasts, and travel …
Dayd
The day equals 24 hours and is the fundamental unit of human routine, calendar…
Weekwk
The week equals 7 days and is the standard cycle for work schedules, school te…
Monthmo
The month averages 30.44 days and is the standard billing, salary, and calenda…
Yearyr
The year equals 365.25 days and is the basic unit for age, contracts, educatio…
Decadedec
The decade equals ten years and is used in historical, cultural, and demograph…
Centuryc
The century equals one hundred years and is the standard unit for major histor…
Speed
Category page →Kilometer per Hourkm/h
Kilometers per hour is the road-speed standard in 195 countries and the univer…
Meter per Secondm/s
Meters per second is the SI speed unit, used in physics, engineering, and Olym…
Mile per Hourmph
Miles per hour is the road-speed standard in the United States, the United Kin…
Knotkn
The knot equals one nautical mile per hour and is the universal speed unit for…
MachMa
Mach is the speed of sound multiplier, used in aviation, missile, and superson…
Foot per Secondft/s
Feet per second is the standard ballistics unit for projectile speeds and Amer…
Centimeter per Secondcm/s
Centimeters per second measures slow phenomena like ocean currents, biological…
Yard per Minuteyd/min
Yards per minute is used in American textile manufacturing and traditional ind…
Inch per Minutein/min
Inches per minute is the American standard for CNC machining feed rates, 3D pr…
Beaufort ScaleBft
The Beaufort scale rates wind force from 0 (calm) to 12 (hurricane), used by s…
Energy
Category page →JouleJ
The joule is the base SI energy unit, used in physics, mechanical engineering,…
KilojoulekJ
The kilojoule is the standard unit on European nutrition labels and in mid-sca…
MegajouleMJ
The megajoule is used for measuring fuel energy content, large-scale electrica…
Kilowatt-HourkWh
The kilowatt-hour is the universal billing unit for residential electricity co…
Watt-HourWh
The watt-hour is the standard unit for small-battery capacity, household elect…
Caloriecal
The calorie is the chemistry energy unit, equal to 4.184 joules and used in th…
Kilocaloriekcal
The kilocalorie (called Calorie on US food labels) measures dietary energy in …
British Thermal UnitBTU
The British thermal unit is the standard for American HVAC systems, gas applia…
ElectronvolteV
The electronvolt is the standard energy unit in atomic physics, particle physi…
Thermthm
The therm equals 100,000 BTU and is the standard unit for natural gas billing …
Pressure
Category page →PascalPa
The pascal is the base SI pressure unit, used in scientific publications and m…
KilopascalkPa
The kilopascal is the standard pressure unit on tire labels, weather forecasts…
MegapascalMPa
The megapascal is the engineering high-pressure unit, used in hydraulics, mate…
Barbar
The bar is the everyday pressure unit in European tire pressures, hydraulics, …
Millibarmbar
The millibar is the legacy meteorology unit, identical to hectopascal, still c…
Pound per Square Inchpsi
PSI (pounds per square inch) is the standard for American tire pressures, hydr…
Atmosphereatm
The atmosphere equals average sea-level pressure and is used in chemistry, div…
Millimeter of MercurymmHg
The millimeter of mercury is the standard medical unit for blood pressure meas…
TorrTorr
The torr equals one millimeter of mercury and is used in vacuum-system specifi…
Inch of MercuryinHg
The inch of mercury is the American aviation standard for altimeter settings a…
Power
Category page →WattW
The watt is the base SI power unit, used worldwide for light bulbs, electrical…
KilowattkW
The kilowatt is the standard power rating for European cars, household applian…
MegawattMW
The megawatt rates power plants, large industrial facilities, and grid-scale r…
Mechanical Horsepowerhp
Horsepower is the American and British unit for car engines, motorcycles, and …
Metric HorsepowerPS
The Pferdestärke (PS) is the metric horsepower unit used in European car marke…
BTU per HourBTU/h
BTU per hour is the standard rating for American heating, air-conditioning, an…
Foot-Pound per Secondft·lbf/s
The foot-pound per second is the American mechanical-power unit, used in engin…
Volt-AmpereVA
The volt-ampere measures AC apparent power, used in transformer ratings, UPS s…
Data
Category page →Bitb
The bit is the smallest unit of digital information, used in network speeds an…
ByteB
The byte equals 8 bits and is the smallest addressable storage unit in modern …
KilobyteKB
The kilobyte equals 1,000 bytes and was the standard file size for documents a…
MegabyteMB
The megabyte is the everyday unit for image files, songs, and small documents …
GigabyteGB
The gigabyte is the standard unit for smartphone storage, mobile data plans, a…
TerabyteTB
The terabyte is the standard unit for hard drives, video archives, and consume…
PetabytePB
The petabyte rates large data centers, scientific archives, and major social-m…
Megabit per SecondMbps
Megabits per second is the standard unit for internet speeds, network bandwidt…