---
title: UnitIlluminance
framework: foundation
role: symbol
role_heading: Class
path: foundation/unitilluminance
---

# UnitIlluminance

A unit of measure for illuminance.

## Declaration

```swift
class UnitIlluminance
```

## Overview

Overview You typically use instances of UnitIlluminance to represent specific quantities of illuminance using the NSMeasurement class. Illuminance Illuminance is the luminous flux incident on a surface. The SI unit for illuminance is the lux (lx), which is derived as one lumen per square meter (1lm / 1m2). The UnitIlluminance class defines its baseUnit() as lux.  |  |   |  |

## Topics

### Accessing the Base Unit

- [baseUnit()](foundation/dimension/baseunit().md)

### Accesing Predefined Units

- [lux](foundation/unitilluminance/lux.md)

## Relationships

### Inherits From

- [Dimension](foundation/dimension.md)

### Conforms To

- [CVarArg](swift/cvararg.md)
- [CustomDebugStringConvertible](swift/customdebugstringconvertible.md)
- [CustomStringConvertible](swift/customstringconvertible.md)
- [Equatable](swift/equatable.md)
- [Hashable](swift/hashable.md)
- [NSCoding](foundation/nscoding.md)
- [NSCopying](foundation/nscopying.md)
- [NSObjectProtocol](objectivec/nsobjectprotocol.md)
- [NSSecureCoding](foundation/nssecurecoding.md)
- [Sendable](swift/sendable.md)
- [SendableMetatype](swift/sendablemetatype.md)

## See Also

### Energy, Heat, and Light

- [UnitEnergy](foundation/unitenergy.md)
- [UnitPower](foundation/unitpower.md)
- [UnitTemperature](foundation/unittemperature.md)