Lm vs. Lumen — What's the Difference?
By Fiza Rafique & Maham Liaqat — Updated on May 6, 2024
Lm (lumen) measures light output from a source, indicating total visible light emitted, while lux measures light intensity per square meter.
Difference Between Lm and Lumen
Table of Contents
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Key Differences
Lumen (lm) quantifies the total visible light emitted by a light source, capturing the overall brightness emitted. On the other hand, lux measures the intensity of light that reaches a surface, reflecting how much of that light illuminates a specific area.
Lumen values help in understanding the light output regardless of its distribution or the area it covers. Whereas lux takes into account the area over which the light is spread, making it crucial for determining how well-lit a specific location will be.
When choosing lighting for a space, lumen values are crucial to assess the total light output available. On the other hand, lux values are used to ensure sufficient illumination is provided in workspace environments, such as offices or classrooms.
Lighting products typically list their light output in lumens, which helps consumers compare the brightness of different lighting options. Conversely, lux measurements are often used in planning and design, ensuring specific areas receive adequate light levels per square meter.
While lumens measure the total light emitted, lux measurements are influenced by the distance the light travels from the source to the surface, demonstrating how brightness perception changes with distance.
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Comparison Chart
Definition
Measures total visible light output from a source
Measures intensity of light on a surface
Unit of Measurement
Lumens
Lux (lumens per square meter)
Primary Use
Comparing brightness of light sources
Ensuring adequate illumination in spaces
Dependence
Independent of distance and area
Depends on area and distance from the light source
Application
General lighting comparison
Specific area lighting requirements
Compare with Definitions
Lm
A unit of luminous flux equal to the light emitted in a unit solid angle by a uniform point source of one candela.
A 100-watt bulb emits about 1600 lumens.
Lumen
Varies with distance from the light source and the area it covers.
Lux levels decrease as the distance from the light source increases.
Lm
Reflects the total light output visible to the human eye from a light source.
LED lights are efficient in providing more lumens per watt.
Lumen
A unit of measurement for illuminance, equal to one lumen per square meter.
An office space typically requires about 500 lux.
Lm
Independent of the area over which the light is dispersed.
Lumens remain constant regardless of how far the light spreads.
Lumen
Used to ensure specific parts of a space are adequately lit.
Reading areas require higher lux to prevent eye strain.
Lm
The measure used to quantify the total amount of visible light emitted by a source.
Higher lumens indicate a brighter light source.
Lumen
Measures how much luminous flux is spread over a given area.
Lower lux might indicate insufficient light for detailed tasks.
Lm
Commonly used to compare the brightness of different lighting products.
When replacing bulbs, check the lumens to ensure sufficient brightness.
Lumen
Critical in environments where precise lighting is crucial, like in laboratories.
High lux levels are maintained in lab environments for accuracy.
Lm
A unit of luminous flux equal to the amount of light given out through a solid angle of 1 steradian by a point source of 1 candela intensity radiating uniformly in all directions
Lumen
The SI unit of luminous flux, equal to the amount of light emitted per second in a unit solid angle of one steradian from a uniform source of one candela.
Lumen
The central cavity of a tubular or other hollow structure in an organism or cell
The stomach empties food into the lumen of the small intestine
Lumen
(Anatomy) The inner open space or cavity of a tubular organ, as of a blood vessel or an intestine.
Lumen
(Biology) The interior of a membrane-bound compartment or organelle in a cell.
Lumen
Abbr. lm(Physics) The SI unit of luminous flux, equal to the amount of light per unit time passing through a solid angle of one steradian from a light source of one candela intensity radiating equally in all directions. See Table at measurement.
Lumen
(physics) In the International System of Units, the derived unit of luminous flux; the light that is emitted in a solid angle of one steradian from a source of one candela. Symbol: lm.
Lumen
(anatomy) The cavity or channel within a tube or tubular organ.
Lumen
(botany) The cavity bounded by a plant cell wall.
Lumen
(medicine) The bore of a tube such as a hollow needle or catheter.
Lumen
A unit of illumination, being the amount of illumination of a unit area of spherical surface, due to a light of unit intensity placed at the center of the sphere.
Lumen
An opening, space, or cavity, esp. a tubular cavity; a vacuole.
Lumen
A unit of luminous flux equal to the amount of light given out through a solid angle of 1 steradian by a point source of 1 candela intensity radiating uniformly in all directions
Lumen
A cavity or passage in a tubular organ;
The lumen of the intestine
Common Curiosities
What is a lumen?
A lumen is a unit of luminous flux and measures the total amount of visible light emitted by a source.
Can you have high lumens but low lux?
Yes, if light is spread over a larger area, it can result in high lumens but low lux levels.
How do lumens and lux differ in practical use?
Lumens measure total light output, useful for evaluating bulb brightness, while lux measures how well a space is illuminated.
Is it better to have more lumens or more lux for a workspace?
More lux is typically better for workspaces as it ensures adequate light on work surfaces.
Why is knowing lumens important when buying bulbs?
Knowing the lumens helps determine how bright the bulb will be.
What is a good lux level for a classroom?
A classroom typically requires about 500 lux for optimal visibility and comfort.
What does lux measure?
Lux measures the intensity of light that falls on a surface, calculated as lumens per square meter.
Can different light sources with the same lumens have different lux values?
Yes, different light sources can emit light differently, affecting how the light is distributed and the resulting lux.
How do you convert lumens to lux?
To convert lumens to lux, divide the number of lumens by the area in square meters over which the light is spread.
What role does distance play in lux measurements?
Distance affects lux measurements because light intensity decreases as distance from the light source increases.
How does one measure lux levels in a room?
Lux levels can be measured using a lux meter, which assesses the intensity of light in an area.
What factors affect the conversion of lumens to lux?
The area and the distance from the light source to the surface impact the conversion.
How does one increase lux without changing lumens?
Increasing lux without changing lumens can be achieved by reducing the area the light covers or bringing the light source closer.
Do lumens affect energy efficiency?
Lumens themselves don't affect efficiency but indicate how much light you get per watt of power consumed.
What is typically higher in outdoor environments, lumens or lux?
Outdoor environments generally have higher lumens due to natural light, but lux can vary significantly depending on the area and shading.
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Written by
Fiza RafiqueFiza Rafique is a skilled content writer at AskDifference.com, where she meticulously refines and enhances written pieces. Drawing from her vast editorial expertise, Fiza ensures clarity, accuracy, and precision in every article. Passionate about language, she continually seeks to elevate the quality of content for readers worldwide.
Co-written by
Maham Liaqat
