# Units and Measurement Label numeric quantities with physical dimensions to allow locale-aware formatting and conversion between related units. ## Topics ### Essentials [`Measurement`](/documentation/Foundation/Measurement) A numeric quantity labeled with a unit of measure, with support for unit conversion and unit-aware calculations. [`NSMeasurement`](/documentation/Foundation/NSMeasurement) A numeric quantity labeled with a unit of measure, with support for unit conversion and unit-aware calculations. [`Unit`](/documentation/Foundation/Unit) An abstract class representing a unit of measure. [`Dimension`](/documentation/Foundation/Dimension) An abstract class representing a dimensional unit of measure. ### Conversion [`UnitConverter`](/documentation/Foundation/UnitConverter) An abstract class that provides a description of how to convert a unit to and from the base unit of its dimension. [`UnitConverterLinear`](/documentation/Foundation/UnitConverterLinear) A description of how to convert between units using a linear equation. ### Physical Dimension [`UnitArea`](/documentation/Foundation/UnitArea) A unit of measure for area. [`UnitLength`](/documentation/Foundation/UnitLength) A unit of measure for length. [`UnitVolume`](/documentation/Foundation/UnitVolume) A unit of measure for volume. [`UnitAngle`](/documentation/Foundation/UnitAngle) A unit of measure for planar angle and rotation. ### Mass, Weight, and Force [`UnitMass`](/documentation/Foundation/UnitMass) A unit of measure for mass. [`UnitPressure`](/documentation/Foundation/UnitPressure) A unit of measure for pressure. ### Time and Motion [`UnitAcceleration`](/documentation/Foundation/UnitAcceleration) A unit of measure for acceleration. [`UnitDuration`](/documentation/Foundation/UnitDuration) A unit of measure for a duration of time. [`UnitFrequency`](/documentation/Foundation/UnitFrequency) A unit of measure for frequency. [`UnitSpeed`](/documentation/Foundation/UnitSpeed) A unit of measure for speed. ### Energy, Heat, and Light [`UnitEnergy`](/documentation/Foundation/UnitEnergy) A unit of measure for energy. [`UnitPower`](/documentation/Foundation/UnitPower) A unit of measure for power. [`UnitTemperature`](/documentation/Foundation/UnitTemperature) A unit of measure for temperature. [`UnitIlluminance`](/documentation/Foundation/UnitIlluminance) A unit of measure for illuminance. ### Electricity [`UnitElectricCharge`](/documentation/Foundation/UnitElectricCharge) A unit of measure for electric charge. [`UnitElectricCurrent`](/documentation/Foundation/UnitElectricCurrent) A unit of measure for electric current. [`UnitElectricPotentialDifference`](/documentation/Foundation/UnitElectricPotentialDifference) A unit of measure for electric potential difference. [`UnitElectricResistance`](/documentation/Foundation/UnitElectricResistance) A unit of measure for electric resistance. ### Concentration and Dispersion [`UnitConcentrationMass`](/documentation/Foundation/UnitConcentrationMass) A unit of measure for concentration of mass. [`UnitDispersion`](/documentation/Foundation/UnitDispersion) A unit of measure for specific quantities of dispersion. ### Fuel Efficiency [`UnitFuelEfficiency`](/documentation/Foundation/UnitFuelEfficiency) A unit of measure for fuel efficiency. ### Data Storage [`UnitInformationStorage`](/documentation/Foundation/UnitInformationStorage) A unit of measure for quantities of information. ### Formatting Measurements [`MeasurementFormatUnitUsage`](/documentation/Foundation/MeasurementFormatUnitUsage) A type that provides the generalized usage for a formatted measurement. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)