Illuminance Converter
Convert illuminance between lux, foot-candles, phot, and other units.
Converter guide
About Illuminance Converter
Illuminance measures light arriving on a surface per unit area. This converter changes units such as lux and foot-candles, helping translate lighting recommendations and meter readings between metric and customary systems.
How to use this converter
- 1Enter the illuminance value measured or listed in a specification.
- 2Choose its source unit and the target unit, checking that the value describes light on a surface rather than light emitted by a source.
- 3Read the result and keep the measurement location, surface orientation, and lighting conditions in mind.
Conversion method and technical details
Lux is one lumen per square meter. A foot-candle is one lumen per square foot, and 1 foot-candle is about 10.764 lux. Other supported units use fixed relationships to the same illuminance quantity.
Worked real-world example
An illuminance of 100 lux is about 9.29 foot-candles. Both describe the same incident light level on the measured surface.
Common scenarios and use cases
Compare workplace or room lighting targets, translate light-meter readings, and work with photographic or building specifications.
For a dependable comparison, confirm both unit labels, keep the original measurement with the converted value, and use the precision required by the task. The converter changes the representation of a value; it does not measure the item or decide which standard your project requires.
Important details and limitations
Illuminance does not describe color quality, glare, uniformity, or a person's visual comfort. Meter position and orientation affect readings. Follow the relevant lighting standard for work or safety decisions.
Check the output unit as well as the number. If the result will be reused in another calculation, retain full precision where possible and round only at the end. For measurements governed by a technical specification, use the standard and tolerance required by that document.
Frequently asked questions
What does lux measure?
It measures luminous flux arriving per square meter of surface.
How many lux equal one foot-candle?
Approximately 10.764 lux.
Does illuminance tell how bright a lamp appears?
No. It describes light on a surface; perceived brightness and source luminance are different quantities.
Why can the converted number look much larger or smaller?
Different units use different scales. A measurement can have a larger number in a smaller unit and still describe the same quantity. Check the source and target unit labels before comparing values.
How many decimal places should I keep?
Keep enough precision for the job and avoid rounding values between steps. Round the final displayed answer to match the specification, document, or measuring tool you are using.