About the Lux to Candela Calculator
This calculator converts lux to cd. lux is lumens per square metre, the amount of light that actually lands on a surface, and cd is candela, the brightness of a light in one particular direction. It multiplies the illuminance by the square of the distance, converting feet to metres if you choose feet. Enter your figures and the answer appears at once, together with a few related values, and you can copy the result with one tap. The sums are done in your browser and nothing is sent anywhere.
Updated October 2026
How to use the Lux to Candela Calculator
- 1Enter the value in lux.
- 2Fill in the other boxes that the lux to cd calculation needs, such as time, voltage or power factor.
- 3Read the answer in the large result box.
- 4Check the extra rows for related values.
- 5Press Copy result to keep it.
When you need lux to cd
A light meter tells you how much light reaches a surface in lux. The lamp's own brightness in a given direction is its intensity in candela. To get from one to the other you must know how far the meter was from the light, because the same lamp gives less lux at a greater distance.
Lighting designers use it to estimate the intensity of a spotlight from a measurement, or to predict the lux at another distance. Photographers use it to compare lights, and students use it to practise the inverse-square law.
How the lux to cd sum works
Candela = lux × distance², with the distance in metres. A reading of 200 lux at 2 m from a small light means an intensity of 200 × 2² = 800 cd.
The displayed answer is rounded to six significant figures, but the sum itself is not rounded, so converting lux to cd and back again gives you the number you started with.
- Measure facing the light
- Use a point-like source
- Double the distance, quarter the lux
Mistakes to avoid when converting lux to cd
The formula applies to a small source viewed from a distance several times larger than the lamp. For large panels or very close readings it is only an estimate. Measure straight in front of the light, with the sensor facing it.
On phone and computer
On a phone, type in the boxes one after another and read the cd result underneath; the Copy button puts it on the clipboard for a message or a note. On a computer the inputs sit on the left and the answer on the right, so you can change one figure and watch the cd value move. The lux to cd page works the same on both. The distance matters here, so double-check it before you trust the answer. Candela to Lumens Calculator and Lumens to Candela Calculator cover total light output, Lumens to Lux Calculator spreads it over an area, and Footcandle to Lux Converter handles imperial units.
Features
- lux to cd in one step
- Related values shown with the answer
- Clear messages for impossible inputs
- Copy the result with one tap
- Private: nothing is uploaded
- Works on phone and computer
Frequently asked questions
How do I convert lux to cd?
Candela = lux × distance², with the distance in metres. A reading of 200 lux at 2 m from a small light means an intensity of 200 × 2² = 800 cd.
What is the formula for lux to cd?
Candela = lux × distance², with the distance in metres. The calculator applies it exactly and rounds only the displayed answer.
What is the difference between lux and cd?
lux is lumens per square metre, the amount of light that actually lands on a surface. cd is candela, the brightness of a light in one particular direction. They measure different things, which is why converting from lux to cd needs more than a simple multiplication in some cases.
What is the inverse-square law?
The illuminance from a small light falls with the square of the distance. Double the distance and you get a quarter of the lux.
Can I use feet?
Yes. Choose feet as the distance unit, and the tool converts to metres before the calculation.
Is this lux to cd calculator free and private?
Yes. It is free, needs no account, and runs in your browser, so the figures you type are not uploaded or stored. It is meant for planning and learning; for wiring or safety work, check the result against your equipment's rating plate and local rules.