Candela vs Lux vs Lumens: The Ultimate Guide

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In the intricate realm of illumination engineering, the comprehension and utilization of lighting metrics are the bedrock upon which effective lighting solutions are crafted. Lighting metrics are the quantitative language through which we assess, analyze, and optimize the luminous characteristics of spaces, objects, and environments. They provide professionals with the tools to engineer lighting systems that meet functional requirements and enhance aesthetics, ambiance, and human experience.

Amidst the diverse lighting metrics, three fundamental measures stand out: Candela, Lux, and Lumens. These metrics, each distinct in purpose and application, collectively form the cornerstone of lighting design and evaluation. Understanding the nuances of Candela, Lux, and Lumens empowers lighting designers, engineers, architects, and practitioners across various disciplines to navigate the complexities of illumination with precision and expertise. As we embark on this exploration, we delve into the essence of Candela, Lux, and Lumens, unraveling their significance and elucidating their roles in shaping the luminous landscape of our surroundings.

Table of Contents

Suppose you’ve ever felt overwhelmed while shopping for LED lights, unsure about the significance of these units; fear not! This article serves as your guide to grasping the importance of these units, enabling you to make well-informed decisions when choosing LED lighting to meet your specific needs.

Navigating the realm of LED light purchases can be challenging, particularly when faced with the intricacies of light intensity measurement units. This challenge is amplified when shopping online without the guidance of an expert. Candela, Lumens, and Lux are commonly featured on the labels of lighting products, serving as crucial indicators of brightness and intensity.

While the terminology might initially appear confusing, this guide is designed to unravel the complexity. We will thoroughly explain each unit, highlighting their roles and applications. By the end of this article, you’ll comprehend these units and be equipped with the knowledge to select the most suitable lamp for your project.

Furthermore, we’ll explore the interplay between Candela, Lux, and Lumens, offering a quick overview to elucidate the relationships among these crucial metrics. So, buckle up as we embark on a journey to decode the language of light measurement units, ensuring that your next LED purchase is a well-informed and confident decision.

Candela Lumens Lux

Candela Explained

Candela, represented as “cd,” plays a pivotal role as an essential SI unit in the International System of Units, employed for quantifying the light intensity emitted by a source in a designated direction. The term “candela” itself derives from a Latin word that translates to candlelight, symbolizing its historical association with the illumination produced by a single wax candle.

Within the International System of Units (SI) framework, Candela is a metric that gauges the perceived brightness of light emitted by a source in a particular direction. The concept of Candela is rooted in human visual perception, acknowledging the varying sensitivity of the human eye to different wavelengths of light.

Candela measures luminous intensity, emphasizing the power of light emitted in a particular direction. The measurement is intricately tied to the human eye’s sensitivity to different wavelengths, emphasizing the green-yellow region. This unique approach ensures that Candela accurately represents how humans perceive brightness, offering a standardized measure that aligns with visual perception.

The calculation of Candela involves accounting for the radiant flux emitted by a light source and the solid angle within which the light is emitted. The resulting unit, expressed in candelas (cd), provides a standardized measure of luminous intensity.

While initially rooted in the concept of candlelight, the modern definition of Candela is more intricate. In essence, it quantifies the total amount of light emitted in a designated direction, with the directionality corresponding to the beam angle of the light source. In straightforward terms, Candela signifies the luminous intensity of a light source, with the unit “1 cd” roughly corresponding to the illumination produced by a typical wax candle.

Consider a standard 25 Watts fluorescent bulb emitting approximately 135 cd in all directions for practical reference. However, if the light beam is narrowed to a 20⁰ beam angle, the intensity increases to around 18,000 cd. This example illustrates a fundamental principle: the narrower the beam angle, the higher the number of candelas produced, resulting in a brighter, more focused illumination.

Understanding Candela is pivotal in various applications, ranging from everyday lighting scenarios to specialized fields like theater lighting, automotive headlights, and architectural illumination. By grasping the concept of Candela and its relationship with beam angle, professionals can make informed decisions to achieve optimal brightness and visibility in diverse lighting environments.

Lumens Unveiled

Lumen, represented by the symbol “lm,” stands as the predominant unit in the lighting industry, encompassing the entirety of luminous flux emanating from a light source. Its definition includes the total amount of light emitted by a lighting source in all directions, representing the overall visible light perceived by the human eye. Unlike Candela, Lumen is not contingent upon a specific direction, offering a comprehensive measure of visible light output.

Lumens quantify luminous flux, which refers to the total amount of visible light emitted by a light source. This measurement considers the entire spectrum of light visible to the human eye. The calculation of Lumens involves considering the spectral sensitivity of the human eye across different wavelengths, providing a weighted measure that aligns with human perception. Lumens offers a standardized and objective metric for comparing the brightness of other light sources.

Comparatively, Lumens and candelas can be juxtaposed. To illustrate, envision a flashlight generating 1 cd of light intensity within a specific beam angle and 12.5 lm of luminous flux. If you obstruct half of the lamp, the same 1 cd source will produce 6.25 lumens. A standard 45 W LED bulb emits approximately 450 lumens of light in a practical scenario. As we progress through this guide, we will delve into the interconnection among these units and elucidate their significance in the lighting field.

Lumens, Candela, and Lux are interrelated metrics within the lighting domain, each serving distinct purposes. While Candela measures luminous intensity in a specific direction, Lux assesses surface illuminance, and Lumens quantifies the total visible light output. Comparing Lumens with Candela, Lumens provide a holistic measure of luminous flux without being confined to a specific direction, making it suitable for evaluating the overall brightness of a light source.

Comparing Lumens with Lux highlights the difference between the total visible light output and the illuminance on a specific surface area. Lux is derived from Lumens but considers the spread of light over a designated location. Grasping these interconnections is essential for lighting design and engineering professionals, empowering them to make well-informed decisions tailored to the specific requirements of a given application.

Lux Demystified

Lux, an integral unit within the lighting metrics, is the illuminance measurement or the amount of light falling on a surface per unit area. Simply put, 1 lux equals 1 lumen per unit area or 1 lm/m2. Represented as “lx,” Lux considers the light source’s luminous intensity, the distance from the source, and the spread of light over a specific area. This comprehensive metric is a crucial indicator of how effectively a given space is illuminated.

For an observer, Lux translates into the perceived brightness of a particular surface area when illuminated by a lamp. The application of Lux follows the inverse-square law, indicating that at a distance tripled from the light source, Lux diminishes to 1/9th as the light is distributed over nine times the area.

This principle underscores the importance of light distribution, where a broader area covered by light results in weaker illumination compared to smaller areas with more concentrated light intensity. LED fixtures employ reflectors designed to control the spread of light over larger surfaces, effectively preventing unnecessary light wastage and ensuring optimal illumination where it is needed.

The relationship between Lux and Candela is intricate, as Lux is a measure derived from Candela, distance, and angle. Lux quantifies the illumination on a surface, factoring in the luminous intensity of the light source and the distance from the source. The Lux formula entails the division of luminous flux, measured in lumens, by the surface area expressed in square meters. Understanding this relationship is pivotal in designing lighting systems that provide adequate brightness and ensure uniformity across a designated location.

Lux finds widespread application in diverse practical scenarios, offering valuable insights into lighting quality in various environments. In architectural lighting design, Lux measurements are critical for achieving optimal brightness levels in offices, classrooms, and retail establishments. Lux is also instrumental in outdoor lighting applications, determining the appropriate illuminance levels for streets, pathways, and public spaces.

Moreover, Lux measurement plays a pivotal role in ensuring safety and compliance with industry standards. In industrial settings, Lux assesses workspaces and guarantees sufficient lighting for tasks that demand precision. In photography and cinematography, Lux is essential for achieving the desired exposure and capturing high-quality images.

What Are The Differences: Candela Vs. Lumens Vs. Lux

Now that you’ve acquired a foundational understanding of these units, it’s important to dispel the assumption that more lumens invariably equate to better light. Opting for the most suitable lighting for your project necessitates a nuanced consideration of candela, lumens, and Lux in tandem.

The Importance of Familiarity with These Units

Given the array of lighting sources available, ranging from LEDs to fluorescents and incandescents, each illuminating spaces differently, it becomes imperative to discern which suits your project best. A comprehensive consideration of candela, lumens, and Lux proves invaluable when devising an effective lighting design for a given space.

Measuring Light Using These Units

Determining the luminous intensity of light sources poses a challenge and is typically undertaken in specialized research laboratories. Manufacturers subsequently provide these values on the packaging of lighting products. Equipped with the knowledge provided in this guide, you can adeptly compare metrics among various lighting products, empowering you to make well-informed decisions customized to the specific requirements of your project.

1. The Relationship: Lumens and Candela

Lumens serve as a metric for luminous flux and are primarily employed by manufacturers to convey the inherent capacity of a light source. For instance, a fixture labeled 100 lm signifies that the lamp can emit this amount of light in all directions, indicating its overall brightness potential.

However, lumens alone do not account for the intricacies of a product’s design and geometry, including the placement of reflectors and light intensity in specific directions. Consequently, lumens exclusively pertain to the rating of bulbs, offering a partial representation of a light source’s luminous potential. It is essential to bear this in mind, as the lumens rating may need to provide a comprehensive overview of the light source’s performance. To illustrate this concept further, please refer to the image below for enhanced clarity.


While lumens delineate the overall raw potential output of light, candela takes a different approach by specifying the intensity of that light in a particular direction and angle. Candela encapsulates the light’s volume and power, providing a more nuanced perspective.

The angle, measured in steradians, represents a three-dimensional angle formed within a sphere by opening a cone and projecting an area equivalent to the square of the radius. The image below illustrates the specific area corresponding to one candela, emphasizing the directional and angular characteristics of measuring light intensity.


A substantial candela rating proves advantageous when concentrating light on a specific target, particularly in art galleries, spotlights, architectural facades, and vehicle headlights. Notably, one candela equals one lumen per steradian, establishing a straightforward relationship between Lumens and Candela, where 1 Candela is equivalent to 12.57 Lumens.

However, caution is warranted when directly comparing candela to lumens. This is because specific light sources, like regular laser lights, may exhibit a minimal lumen value despite having a substantial candela rating. The nature of these light sources highlights the importance of considering both metrics to understand their performance in different applications comprehensively.

2. The Relationship: Lumens and Lux

When selecting two LED lamps with an identical 100 lumens rating, their brightness may not be equivalent. The reason is overseeing factors such as reflectors and fixture design significantly influence light distribution.

This is where Lux proves invaluable. Lux is a practical unit for measuring light, explicitly defining the quantity of light on a designated surface area. Typically measured about 10 meters away within 1 square foot of a wall, Lux offers insight into how a one-square-meter area is illuminated, equivalent to 1 flux.


Consider a spotlight as an illustration; it would exhibit a high Lux value as it concentrates light within a confined area and projects it over longer distances. Conversely, a spread light covering a more extensive surface area might have a lower Lux value, even if its lumens are comparable to the spotlight. The critical influence in this scenario lies in the design and engineering of the fixture. Understanding the importance of achieving the correct Lux value is essential for optimal lighting.

Numerous online conversion calculators are available to facilitate the conversion of values between candela, lumens, and Lux, providing useful approximations for these lighting metrics.

Foot Candles

It represents a non-SI unit for illuminance, akin to Lux, and is characterized by its dependence on an area. Specifically, one lumen per square foot is equivalent to one foot-candle. Although less prominently featured than other lighting metrics, it finds application in certain regions for lighting layout purposes.

3. Compare: Lumens and Watts

When perusing a lighting store, the term “watts” will likely catch your eye when evaluating lamps. However, it is imperative to recognize that watts do not serve as a unit for measuring light; instead, they quantify the power consumed by a lamp, denoted by “W.”

It’s important to note that a 1W LED will generate more light (lumens) compared to a 1W halogen light. This discrepancy arises from the superior energy efficiency of LEDs. Higher wattage consumption in traditional lighting sources, such as halogen lights, often leads to elevated heat production, resulting in substantial energy loss. Discerning the difference between watts and light output is essential for making informed decisions regarding lighting selections and optimizing energy efficiency.

Luminous Efficacy

Luminous Efficacy, a measure of efficiency, gauges how effectively a light source produces illumination. It is determined by dividing luminous flux by power consumption, expressed as Lumens/Watts. A higher efficacy indicates a more efficient light source that produces brighter illumination.

Selecting the most suitable measuring unit for light depends on your specific needs.

For illuminating a room, lamps with higher lumen ratings are preferable. Conversely, prioritizing higher candela and lux values is essential if you aim to accentuate architectural features or focus on particular elements. By aligning your lighting selections with the goals of your business project and applying the insights offered in this guide, you can make informed decisions to acquire optimal lighting solutions for your needs.

Influencing Factors on the Values of Candela, Lux, and Lumens

The values of Candela, Lux, and Lumens are influenced by several factors, including:

1. Distance

The distance between an object and the light source significantly impacts Lux and Lumen’s values. This is due to the inverse square law, where doubling the distance decreases Lux values to 1/4th of the initial values. However, Candela’s values remain unaffected regarding angles rather than distance.

2. Angle Of Radiance

The angle produced by the light source plays a crucial role in determining illumination. Smaller angles result in higher values of Candela and Lux, creating brighter light. Additionally, larger angles of radiance lead to an increase in the illuminated area while keeping the Lumens value constant.

3. Luminous Efficiency

Luminous efficiency gauges the ability of a light source to produce bright lights and is contingent on the Wattage of the power source and the Lumens rating. A higher luminous efficiency is achieved when the Watt value decreases, producing brighter light. In essence, greater luminous efficiency corresponds to increased brightness.

Practical Applications

A. Illuminating Common Scenarios with Candela, Lux, and Lumens

1. Home Lighting Design

In-home lighting design, carefully considering Candela, Lux, and Lumens is paramount. Candela guides the selection of light sources for focused tasks, Lux helps determine the appropriate illuminance levels in various rooms, and Lumens quantifies the overall brightness for aesthetic and functional purposes.

2. Outdoor Street Lighting

Candela is crucial in street lighting applications to ensure the right intensity for visibility and safety. Lux measurements aid in determining uniformity and illuminance levels across roadways. At the same time, Lumens provides an overall brightness assessment for adequate outdoor lighting.

3. Theatrical Stage Lighting

In theatrical lighting, the precise control of Candela is indispensable for creating captivating performances with focused beams. Lux measurements help achieve desired brightness levels on the stage, while Lumens contribute to the overall atmospheric ambiance.

B. How Professionals Leverage these Metrics for Effective Lighting Solutions 

1. Architectural Lighting Designers

Architects leverage Candela, Lux, and Lumens to design lighting solutions that accentuate architectural features. Candela aids in directing attention to specific elements, Lux ensures optimal brightness levels for various areas, and Lumens play a pivotal role in shaping the overall visual impact of the design.

2. Photographers and Cinematographers

Professionals in photography and cinematography rely on these metrics for optimal lighting conditions. Candela assists in creating dynamic highlights and shadows, Lux ensures proper exposure for detailed shots, and Lumens contributes to the overall brightness and mood in visual storytelling.

3. Industrial and Workplace Lighting

In industrial settings, professionals use Candela to focus light on specific work areas, Lux to maintain adequate illuminance levels, and Lumens to optimize overall brightness. This ensures efficient and safe working environments by tailoring lighting solutions to specific tasks.

4. Urban Planners and City Designers

Candela, Lux, and Lumens play a crucial role in urban planning, where professionals aim to create well-lit and aesthetically pleasing cityscapes. These metrics guide decisions on street lighting intensity, public space illumination, and overall city ambiance.

5. Retail and Visual Merchandisers

In retail settings, professionals use these metrics to enhance the shopping experience. Candela helps highlight products, Lux ensures appropriate brightness in display areas, and Lumens contributes to creating inviting and visually appealing retail spaces.

Challenges and Misconceptions

A. Common Misunderstandings about Candela, Lux, and Lumens

1. Equating Watts with Brightness
One prevalent misconception is equating watts with the brightness of a light source. This misunderstanding overlooks that watts measure power consumption, not light output. Addressing this misconception is crucial for making informed decisions about energy-efficient lighting.

2. Neglecting Angle and Directionality
Another common misunderstanding involves paying attention to the influence of angle and directionality on Candela’s values. It’s essential to recognize that Candela is contingent on the direction in which light is emitted, impacting the perceived brightness of the source.

3. Overemphasis on Lumens Alone
Many individuals tend to focus solely on Lumens when assessing light output, disregarding the role of Candela and Lux in providing a comprehensive understanding of illumination. This oversight can lead to suboptimal lighting choices, especially when direction and brightness concentration matter.

B. Addressing Challenges in Measuring and Interpreting These Metrics

1. Accurate Measurement Techniques
One challenge is ensuring accurate measurement techniques for Candela, Lux, and Lumens. Professionals need help quantifying these metrics due to factors like variability in light sources and environmental conditions. Standardized measurement procedures and equipment calibration are imperative to mitigate inaccuracies.

2. Interpreting Angle and Directionality
Interpreting the impact of angle and directionality on Candela’s values requires careful consideration. Professionals often grapple with translating these measurements into practical lighting solutions. Improved educational resources and training programs can enhance the industry’s proficiency in effectively interpreting these aspects.

3. Integration of Advanced Technologies
Integrating advanced lighting technologies poses a challenge in keeping up with accurate measurements. The emergence of innovative light sources necessitates continuous advancements in measurement tools and methodologies to ensure relevance and precision.

C. Tips for Overcoming Misconceptions in Real-World Applications

1. Educational Campaigns
Implementing educational campaigns can help dispel common misconceptions about Candela, Lux, and Lumens. These initiatives can target professionals and the general public, fostering a better understanding of the nuanced aspects of lighting metrics.

2. Promoting Comprehensive Training
Providing comprehensive training for professionals in various fields, such as architects, designers, and engineers, is essential. This training should emphasize the interplay between Candela, Lux, and Lumens, enabling practitioners to make informed decisions in real-world applications.

3. Encouraging Multidimensional Evaluation
Encouraging a multidimensional evaluation approach in lighting design and decision-making processes is crucial. Rather than solely relying on Lumens, professionals should consider the synergy between Candela, Lux, and Lumens to create optimal lighting solutions that address functional and aesthetic requirements.


Selecting the right LED lighting solution becomes a straightforward process with the expertise of a reputable LED manufacturer. Communicate your requirements to us, and we’ll offer tailored guidance to fulfill the precise lighting needs of your projects. For further details, feel free to contact Upward Lighting.

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