Conversion of luminance units

Luminance Unit Conversion: Light Up Your World

On this page, dedicated to luminance unit conversions, we will take you on a journey through the world of light and its measurement. Luminance is a key element in the world of physics, lighting design, and photography. Let’s dive into how luminance affects our everyday lives and how we can correctly measure and convert it.

What is Luminance and Why Is It Important?

Luminance is a measure of the brightness of light as perceived by the human eye. It is distinct from other measurements of light, such as illuminance or luminous flux, which do not take human perception into account. Luminance is measured in candelas (cd), which is the base unit of the International System of Units (SI).

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Luminance Units

In addition to candelas, you may also encounter other units, such as lumens (lm) or foot-candles (fc). While lumens measure the total luminous flux of a light source, candelas focus on its intensity in a particular direction.

What is the Difference Between Candela and Lumen?

Candela (cd): A candela is the unit of luminance in the International System of Units (SI). Luminance refers to the intensity of light in a particular direction and is defined in terms of the human perception of light. One candela is equal to the luminance of a source that emits monochromatic radiation at a frequency of 540×10^12 hertz and has a luminous flux of 1/683 watts per steradian.

Lumen (lm): A lumen is the unit of luminous flux, which is the total amount of light emitted by a source regardless of direction. Lumens measure the total “amount” of light that a source emits. One lumen is equal to the luminous flux of a source with a luminance of one candela that emits light into a space with an angular width of one steradian.

While candela is therefore a measure of the intensity of light in a particular direction, lumens measure the total amount of light emitted by a source. In practice, lumens are often used to determine the output of light bulbs and fixtures, while candelas are useful for specifying the intensity of light in a particular direction, which is important for example in lighting design or in photometry.

Why Do You Need Luminance Unit Conversions?

In practice, you may encounter different units of luminance depending on the type and origin of the lighting device. For example, when choosing lighting for your home or workplace, you may need to compare the luminance of different types of light bulbs, which may be listed in different units.

Examples of Luminance in Practice


  • For a bedroom, a lower luminance is usually suitable, which creates a calm and relaxing atmosphere. The recommended luminance should be in the range of 10-20 candelas per lamp. This is sufficient for reading or other relaxing activities before bed.

Living room:

  • In a living room, where families spend a lot of time and engage in a variety of activities, a luminance in the range of 20-40 candelas per lamp is suitable. This will ensure adequate visibility for reading, watching TV, or playing games.


  • In a kitchen, a higher luminance is needed for cooking and food preparation. The recommended luminance here can be around 70-80 candelas per main light source to ensure sufficient brightness for safe work.


  • For bathrooms, a luminance in the range of 70-80 candelas is recommended, especially at mirrors, to be able to perform activities such as makeup or shaving with sufficient visibility.

Workshop or workspace:

  • For workshops and workspaces, where it is necessary to see well for detailed work, a recommended luminance in the range of 80-100 candelas per lamp is recommended. Higher luminance helps to prevent eye fatigue and increases work accuracy.

Reading nook:

  • For a reading nook, it is ideal to have a luminance of around 50 candelas, which is sufficient for comfortable reading without excessive glare or eye fatigue.

It is important to note that these values are only approximate and may vary depending on personal preferences and the specific needs of individual spaces. It is also good to combine different light sources (main lighting, task lamps, accent lighting) to achieve the best lighting effect.

Luminance Unit Conversions

Candelas to Lumens

To convert candelas to lumens, use the following formula:

Lumens = Candelas * Steradians