Convert luminous intensity (candela) to illuminance (lux) using distance from the source.
Formula:
Lux = Candela / (Distance²)In the world of lighting design, photography, architecture, and engineering, understanding light measurement is essential. Two commonly used units are candela (cd) and lux (lx). While candela represents luminous intensity in a specific direction, lux measures the amount of light (illuminance) received on a surface. Our Candela to Lux Calculator helps you easily convert luminous intensity to surface illumination using distance as the determining factor.
Candela is the SI unit of luminous intensity. It quantifies how bright a light source appears in a specific direction. One candela is roughly equal to the light emitted by a standard candle. A flashlight or laser pointer often has high candela values because they concentrate light in a focused beam.
Lux is the SI unit of illuminance. It measures the amount of light falling on a surface per unit area. One lux equals one lumen per square meter. Lux helps assess how well a space is lit—for example, offices typically require around 300–500 lux for ideal working conditions.
The lux value depends on two factors: the luminous intensity in candela and the distance from the light source to the illuminated surface.
lux = candela / distance²Where:
This formula assumes that the light hits the surface perpendicularly, and there is no beam spread or losses due to reflection or absorption.
Let’s say you have a light with a luminous intensity of 1000 cd, and the distance to the wall is 2 meters.
lux = 1000 / (2 × 2) = 1000 / 4 = 250 luxThis means the wall receives 250 lux of illumination, which is suitable for general indoor lighting conditions.
| Environment | Recommended Lux |
|---|---|
| Moonlight (full) | 0.1 lux |
| Street lighting | 10–30 lux |
| Home lighting | 100–300 lux |
| Office lighting | 300–500 lux |
| Surgical theater | 10,000 lux |
| Bright sunlight | 100,000 lux |
The core of the conversion formula relies on the Inverse Square Law. As light travels further from its source, it spreads out and becomes less intense.
lux = cd / r² demonstrates that doubling the distance reduces illuminance by a factor of four.
This is essential knowledge for designing energy-efficient lighting systems.
Manual calculations are error-prone and time-consuming. With our Candela to Lux Calculator, you get:
No. Lumen is total light output, while lux is light per square meter (lumen/m²).
No. Distance is essential for this conversion as per the inverse square law.
1 lux. That’s because 1 / 1² = 1.
Use a light meter (lux meter), available as handheld devices or mobile apps.
Because it spreads out in space and its intensity diminishes with the square of the distance.
Many architects and engineers use lux diagrams to plan how light falls across rooms. These maps, combined with lux calculations from candelas, ensure uniform lighting without glare or dark spots.
Whether you're a lighting designer, student, engineer, or enthusiast, converting candela to lux gives you the clarity to design effective and efficient lighting setups. Use our Candela to Lux Calculator to save time, eliminate guesswork, and deliver well-lit spaces for any environment. With just two inputs—intensity and distance—you gain actionable insights into how much light your surface receives.
Bookmark this tool and explore our other calculators to master the art and science of illumination.
Understanding how light spreads from a source helps explain why lux decreases over distance. In reality, light travels in a cone or spherical pattern from a source. The farther it gets from the source, the wider the area it covers—and the thinner its intensity becomes. This concept is critical in lighting design.
For example, if a spotlight emits 1000 candela in a narrow beam, and that beam is projected 1 meter away, it illuminates a smaller area with high lux. At 5 meters, the same beam illuminates a larger area, but each part of that area receives less light per square meter.
To visualize this, imagine using a flashlight on a wall. At 1 meter, the beam is small and bright. As you step back to 3 or 4 meters, the beam gets wider and dimmer. This real-world effect is exactly what the inverse square law explains.
Proper lux levels affect everything from mood and alertness to eye strain and work performance. Insufficient lighting may lead to:
Conversely, well-lit environments tailored to the right lux levels improve focus, visibility, and comfort. Here’s a general guide for lux levels based on activity type:
| Activity | Recommended Lux |
|---|---|
| Casual reading | 150–300 lx |
| Precision assembly work | 1000–1500 lx |
| Warehouse navigation | 100–200 lx |
| Reception area | 200–300 lx |
| Supermarket aisles | 400–700 lx |
| Surgery room | 10,000 lx or more |
We’re constantly working on improving the Candela to Lux Calculator to make it more useful for professionals and learners alike. Upcoming features may include:
To ensure accurate lux estimation or measurement, consider the following practical guidelines:
Many users wonder why both candela and lux are used in lighting terminology. They each serve a unique purpose:
This is especially important in fields like architecture, roadway safety, manufacturing, and retail display setups. For instance, a 500 cd spotlight and a 500 cd floodlight may seem equal, but due to different beam spreads, their lux values can be dramatically different at the same distance.
With increasing emphasis on energy conservation, being precise with lux levels helps avoid over-lighting. Unnecessary high-intensity lighting contributes to:
Using a Candela to Lux Calculator ensures that light is used effectively and responsibly. This is especially critical in sustainable building design, green offices, and smart home lighting systems.
NASA and space agencies carefully plan lighting for spacecraft interiors, habitats, and moon bases. Lux levels are finely tuned to regulate circadian rhythms for astronauts and ensure mission-critical tasks have optimal visibility, often using LED systems with defined candela output to meet lux targets in confined environments.
If you're a student or lighting designer, consider exploring these topics to expand your knowledge:
The Candela to Lux Calculator bridges the gap between theoretical lighting values and real-world illumination. With a simple formula—powered by precise inputs—you can predict how light behaves in any environment. Whether you're illuminating a museum exhibit, designing an energy-efficient workspace, or simply learning the fundamentals, this tool provides a critical advantage in mastering light science.
Try it now and take the guesswork out of lighting design!