Overview
Light units are used in lighting design, photography and displays. This tool brings luminous intensity units (cd) and illuminance units (lux and fc) together while preventing invalid conversions between different quantities.
Formula
For conversions within the same group: converted value = value × source unit factor ÷ target unit factor. 1 fc = 10.7639104 lux, and 1 phot = 10,000 lux.
How it works
Choose the source unit
Decide whether you are measuring luminous intensity or illuminance.
Choose a unit from the same group
For example, cd to mcd, or lux to fc.
Read the result
The converted value appears with reference units from the same group.
Worked examples
Candela to millicandela
1 cd = 1,000 mcd.
Foot-candle to lux
1 fc = 10.7639104 lux.
Frequently asked questions
What is the difference between candela and lux?
Candela measures emitted light intensity in a given direction, while lux measures light falling on a surface area.
Why can't I convert cd to lux directly?
The conversion requires distance from the source, solid angle and surface area. It is not a single fixed factor.
What is a lumen?
Lumen measures total luminous flux. One lumen distributed over a solid angle of 1 steradian gives an intensity of 1 candela.
This calculator is for educational and informational purposes only and is not a substitute for professional advice.