UnitCon API

Free, no-auth REST API for unit and currency conversion. All unit conversions are computed server-side from exact factor tables. Currency rates update every 4 hours from the European Central Bank via Frankfurter.

Endpoint

GET https://unitcon.app/api/convert

Parameters

Param	Type	Description
from	string	Unit ID to convert from (e.g. meter, kilogram, USD)
to	string	Unit ID to convert to (e.g. foot, pound, EUR)
value	number	Numeric value to convert

Examples

Unit conversion

GET https://unitcon.app/api/convert?from=meter&to=foot&value=1.8

{
  "from": "meter",
  "to": "foot",
  "value": 1.8,
  "result": 5.905512,
  "converter": "length",
  "formula": "Multiply meters by 3.28084 to get feet.",
  "timestamp": "2026-05-10T12:00:00.000Z"
}

Currency conversion (ISO 4217 codes, case-insensitive)

GET https://unitcon.app/api/convert?from=USD&to=EUR&value=100

{
  "from": "USD",
  "to": "EUR",
  "value": 100,
  "result": 89.42,
  "converter": "currency",
  "ratesDate": "2026-05-09",
  "formula": null,
  "timestamp": "2026-05-10T12:00:00.000Z"
}

Error response

{
  "error": "Unknown unit pair \"furlongg\" → \"meter\". See https://unitcon.app/api-docs for valid unit IDs.",
  "code": "UNKNOWN_UNIT"
}

Error codes

HTTP	code	Meaning
400	MISSING_PARAMS	from, to, or value is absent
400	INVALID_VALUE	value is not a finite number
422	UNKNOWN_UNIT	from/to pair not found in any converter
422	INVALID_CONVERSION	Conversion produced a non-finite result
429	RATE_LIMITED	More than 100 requests per minute from your IP

Rate limits & caching

100 requests per minute per IP address. Limit headers are returned on every response: X-RateLimit-Limit, X-RateLimit-Remaining, X-RateLimit-Reset.
Unit conversions are cacheable: Cache-Control: public, max-age=3600.
Currency responses carry max-age=14400 (4 hours) to match the ECB publishing schedule.
CORS is open (Access-Control-Allow-Origin: *). No API key required.

Unit IDs

Pass these strings as from and to. Both units must belong to the same converter. Currency uses ISO 4217 codes (e.g. USD, EUR, GBP) and is case-insensitive.

Length(20 units)

meterkilometercentimetermillimetermicrometernanometermileyardfootinchnautical-milelight-yearparsecastronomical-unitfurlongfathomchainrodangstrompicometer

Weight / Mass(12 units)

kilogramgrammilligrammicrogramtonnepoundouncestoneshort-tonlong-toncaratgrain

Volume(18 units)

cubic-meterlitermillilitercubic-centimetercubic-inchcubic-footcubic-yardus-gallonus-fluid-ounceus-quartus-pintus-cupus-tablespoonus-teaspoonimperial-gallonimperial-fluid-ounceimperial-quartimperial-pint

Temperature(4 units)

celsiusfahrenheitkelvinrankine

Area(11 units)

square-metersquare-kilometersquare-centimetersquare-millimetersquare-inchsquare-footsquare-yardsquare-mileacrehectaresquare-nautical-mile

Pressure(11 units)

pascalkilopascalmegapascalbarmillibaratmospherepsitorrmillimeter-of-mercuryinch-of-mercurykgf-per-sq-cm

Energy(13 units)

joulekilojoulemegajoulegigajoulecalorie-thkilocaloriewatt-hourkilowatt-hourmegawatt-hourbtuelectronvoltergfoot-pound

Volume (Dry)(6 units)

cubic-meterus-dry-bushelus-dry-peckus-dry-quartus-dry-pintliter

Power(9 units)

wattkilowattmegawattgigawatthorsepower-mechanicalhorsepower-metricbtu-per-hourcalorie-per-secondfoot-pound-per-second

Force(8 units)

newtonkilonewtonmeganewtonpound-forcekilogram-forcedyneounce-forcepoundal

Time(12 units)

secondmillisecondmicrosecondnanosecondminutehourdayweekmonthyeardecadecentury

Speed(7 units)

meter-per-secondkilometer-per-hourmile-per-hourknotfoot-per-secondmachspeed-of-light

Angle(7 units)

radiandegreegradianarcminutearcsecondturnmilliradian

Fuel Consumption(4 units)

liter-per-100kmkilometer-per-literus-mpguk-mpg

Data Storage(16 units)

bitbytekilobitkilobytemegabitmegabytegigabitgigabyteterabitterabytepetabytekibibytemebibytegibibytetebibytepebibyte

Angular Velocity(4 units)

radian-per-seconddegree-per-secondrevolution-per-minuterevolution-per-second

Acceleration(6 units)

meter-per-second-squaredcentimeter-per-second-squaredfoot-per-second-squaredstandard-gravitygalinch-per-second-squared

Angular Acceleration(4 units)

radian-per-second-squareddegree-per-second-squaredrevolution-per-second-squaredrevolution-per-minute-squared

Density(9 units)

kilogram-per-cubic-metergram-per-cubic-centimetergram-per-millilitergram-per-literkilogram-per-literpound-per-cubic-footpound-per-cubic-inchpound-per-us-gallonounce-per-us-gallon

Specific Volume(5 units)

cubic-meter-per-kilogramcubic-centimeter-per-gramliter-per-kilogramliter-per-gramcubic-foot-per-pound

Moment of Inertia(5 units)

kilogram-meter-squaredgram-centimeter-squaredpound-foot-squaredounce-inch-squaredpound-inch-squared

Moment of Force(6 units)

newton-meterkilonewton-meternewton-centimeterkilogram-force-meterpound-force-footpound-force-inch

Torque(7 units)

newton-meterkilonewton-meternewton-centimeterkilogram-force-meterpound-force-footpound-force-inchdyne-centimeter

Fuel Efficiency (Mass)(6 units)

joule-per-kilogramkilojoule-per-kilogrammegajoule-per-kilogrambtu-per-poundkilocalorie-per-kilogramcalorie-per-gram

Fuel Efficiency (Volume)(7 units)

joule-per-cubic-meterkilojoule-per-cubic-metermegajoule-per-cubic-meterbtu-per-cubic-footbtu-per-us-gallonkilocalorie-per-cubic-metermegajoule-per-liter

Temperature Interval(4 units)

kelvin-intervalcelsius-intervalfahrenheit-intervalrankine-interval

Thermal Expansion(4 units)

per-kelvinper-celsiusper-fahrenheitper-rankine

Thermal Resistance(3 units)

kelvin-per-wattcelsius-per-wattfahrenheit-hour-per-btu

Thermal Conductivity(6 units)

watt-per-meter-kelvinwatt-per-centimeter-kelvinkilowatt-per-meter-kelvinbtu-per-hour-foot-fahrenheitbtu-inch-per-hour-foot-squared-fahrenheitcalorie-per-second-centimeter-celsius

Specific Heat Capacity(5 units)

joule-per-kilogram-kelvinkilojoule-per-kilogram-kelvincalorie-per-gram-celsiuskilocalorie-per-kilogram-celsiusbtu-per-pound-fahrenheit

Heat Density(7 units)

joule-per-cubic-meterkilojoule-per-cubic-metermegajoule-per-cubic-meterbtu-per-cubic-footbtu-per-us-galloncalorie-per-cubic-centimeterkilocalorie-per-cubic-meter

Heat Flux Density(7 units)

watt-per-square-meterkilowatt-per-square-meterwatt-per-square-centimeterbtu-per-hour-square-footbtu-per-minute-square-footcalorie-per-hour-square-centimeterkilocalorie-per-hour-square-meter

Heat Transfer Coefficient(5 units)

watt-per-square-meter-kelvinwatt-per-square-meter-celsiusbtu-per-hour-square-foot-fahrenheitkilocalorie-per-hour-square-meter-celsiuscalorie-per-second-square-centimeter-celsius

Flow (Volumetric)(11 units)

cubic-meter-per-secondcubic-meter-per-minutecubic-meter-per-hourliter-per-secondliter-per-minuteliter-per-hourmilliliter-per-secondus-gallon-per-minuteus-gallon-per-hourcubic-foot-per-secondcubic-foot-per-minute

Mass Flow Rate(9 units)

kilogram-per-secondkilogram-per-minutekilogram-per-hourgram-per-secondgram-per-minutepound-per-secondpound-per-minutepound-per-hourtonne-per-hour

Molar Flow Rate(6 units)

mole-per-secondmole-per-minutemole-per-hourmillimole-per-secondmillimole-per-minutekilomole-per-hour

Mass Flux Density(6 units)

kilogram-per-square-meter-per-secondkilogram-per-square-meter-per-hourgram-per-square-centimeter-per-secondgram-per-square-meter-per-secondpound-per-square-foot-per-secondpound-per-square-foot-per-hour

Molar Concentration(6 units)

mole-per-cubic-metermole-per-litermillimole-per-litermicromole-per-liternanomole-per-litermole-per-deciliter

Solution Concentration(9 units)

kilogram-per-cubic-metergram-per-litermilligram-per-litermicrogram-per-litergram-per-millilitergram-per-deciliterpercent-weight-volumeparts-per-millionparts-per-billion

Dynamic Viscosity(8 units)

pascal-secondmillipascal-secondcentipoisepoisedyne-second-per-square-centimeterpound-per-foot-per-secondpound-per-foot-per-hourkilogram-force-second-per-square-meter

Kinematic Viscosity(8 units)

square-meter-per-secondsquare-centimeter-per-secondsquare-millimeter-per-secondcentistokesstokessquare-foot-per-secondsquare-foot-per-hoursquare-inch-per-second

Surface Tension(5 units)

newton-per-metermillinewton-per-meterdyne-per-centimetererg-per-square-centimeterpound-force-per-foot

Permeability(6 units)

square-metersquare-centimetersquare-millimeterdarcymillidarcymicrodarcy

Luminance(8 units)

candela-per-square-meternitcandela-per-square-centimeterstilbfoot-lambertlambertmillilambertapostilb

Luminous Intensity(4 units)

candelamillicandelakilocandelacandlepower

Illumination(6 units)

luxmilliluxkiloluxfoot-candlephotnox

Digital Image Resolution(6 units)

pixels-per-meterpixels-per-centimeterpixels-per-millimeterdots-per-inchpixels-per-inchdots-per-centimeter

Frequency & Wavelength(10 units)

hertzkilohertzmegahertzgigahertzterahertzmeter-wlcentimeter-wlmillimeter-wlmicrometer-wlnanometer-wl

Electric Charge(8 units)

coulombmillicoulombmicrocoulombnanocoulombpicocoulombampere-hourmilliampere-hourfaraday

Linear Charge Density(6 units)

coulomb-per-metermillicoulomb-per-metermicrocoulomb-per-meternanocoulomb-per-metercoulomb-per-centimetermicrocoulomb-per-centimeter

Surface Charge Density(5 units)

coulomb-per-square-metermillicoulomb-per-square-metermicrocoulomb-per-square-metercoulomb-per-square-centimetermicrocoulomb-per-square-centimeter

Volume Charge Density(5 units)

coulomb-per-cubic-metermillicoulomb-per-cubic-metermicrocoulomb-per-cubic-metercoulomb-per-cubic-centimetermicrocoulomb-per-cubic-centimeter

Electric Current(7 units)

amperekiloamperemilliamperemicroamperenanoamperepicoampereabampere

Linear Current Density(6 units)

ampere-per-meterkiloampere-per-metermilliampere-per-meterampere-per-centimeterampere-per-millimetermilliampere-per-millimeter

Surface Current Density(5 units)

ampere-per-square-meterkiloampere-per-square-metermilliampere-per-square-meterampere-per-square-centimetermilliampere-per-square-millimeter

Electric Field Strength(7 units)

volt-per-meterkilovolt-per-metermegavolt-per-metermillivolt-per-metermicrovolt-per-metervolt-per-centimetervolt-per-millimeter

Electric Potential(8 units)

voltkilovoltmegavoltmillivoltmicrovoltnanovoltabvoltstatvolt

Electric Resistance(6 units)

ohmkilohmmegohmmilliohmmicroohmabohm

Electric Resistivity(6 units)

ohm-metermilliohm-metermicroohm-meterohm-centimetermicroohm-centimeterohm-millimeter-squared-per-meter

Electric Conductance(7 units)

siemensmillisiemensmicrosiemensnanosiemensmhomillimhoabmho

Electric Conductivity(6 units)

siemens-per-metersiemens-per-centimetermillisiemens-per-metermillisiemens-per-centimetermicrosiemens-per-metermicrosiemens-per-centimeter

Capacitance(7 units)

faradmillifaradmicrofaradnanofaradpicofaradabfaradstatfarad

Inductance(6 units)

henrymillihenrymicrohenrynanohenryabhenrystathenry

Magnetomotive Force(4 units)

ampere-turnkiloampere-turnmilliampere-turngilbert

Magnetic Field Strength(4 units)

ampere-per-meterkiloampere-per-metermilliampere-per-meteroersted

Magnetic Flux(5 units)

weberkilowebermilliwebermicrowebermaxwell

Magnetic Flux Density(6 units)

teslamilliteslamicroteslananoteslagaussgamma

Radiation (Effective Dose)(5 units)

sievertmillisievertmicrosievertremmillirem

Radiation Activity(10 units)

becquerelkilobecquerelmegabecquerelgigabecquerelcuriemillicuriemicrocurienanocuriepicocurierutherford

Radiation Exposure(5 units)

coulomb-per-kilogrammillicoulomb-per-kilogrammicrocoulomb-per-kilogramroentgenmilliroentgen

Radiation Absorbed Dose(6 units)

graymilligraymicrograyradmilliraderg-per-gram

SI Prefixes(21 units)

yottazettaexapetateragigamegakilohectodecabase-unitdecicentimillimicronanopicofemtoattozeptoyocto

Data Transfer(9 units)

bit-per-secondkilobit-per-secondmegabit-per-secondgigabit-per-secondterabit-per-secondbyte-per-secondkilobyte-per-secondmegabyte-per-secondgigabyte-per-second

Sound Level(3 units)

decibelbelneper

Typography(7 units)

pointpicainchcentimetermillimeterpixel-96dpiem-16px

Volume – Lumber(6 units)

cubic-metercubic-footcubic-inchboard-footcordcord-foot

Currency rates: Frankfurter / European Central Bank. For informational use only.