| lux | |
|---|---|
 A lux meter for measuring illuminance | |
| General information | |
| Unit system | SI |
| Unit of | illuminance |
| Symbol | lx |
| Conversions | |
| 1 lx in ... | ... is equal to ... |
| SI base units | cd⋅sr⋅m−2 |
| US customary units | 0.0929 fc |
| CGS units | 10−4 ph |
The lux (symbol: lx) is the unit of illuminance, or luminous flux per unit area, in the International System of Units (SI).[1][2] It is equal to one lumen per square metre. In photometry, this is used as a measure of the irradiance, as perceived by the spectrally unequally responding human eye, of light that hits or passes through a surface. It is analogous to the radiometric unit watt per square metre, but with the power at each wavelength weighted according to the luminosity function, a model of human visual brightness perception, standardized by the CIE and ISO.[3] In English, "lux" is used as both the singular and plural form.[4] The word is derived from the Latin word for "light", lux.
- ^ International Bureau of Weights and Measures (2019-05-20), The International System of Units (SI) (PDF) (9th ed.), ISBN 978-92-822-2272-0, archived from the original on 2021-10-18
- ^ CIE (2020). CIE S 017:2020 ILV: International Lighting Vocabulary, 2nd edition (2 ed.). CIE.
- ^ ISO/CIE 23539:2023 CIE TC 2-93 Photometry — The CIE system of physical photometry. ISO/CIE. 2023. doi:10.25039/IS0.CIE.23539.2023.
- ^ NIST Guide to SI Units. Chapter 9 – Rules and Style Conventions for Spelling Unit Names, National Institute of Standards and Technology.