Lumens Calculator

Calculating lumens is essential for determining the amount of light needed for a specific area. Lumens measure the total quantity of visible light emitted by a source.

Steps to Calculate Lumens

Measure the Area: Determine the dimensions of the area you want to illuminate. Calculate the area in square meters (or square feet).
Determine the Lux Requirement: Lux is the measurement of light intensity. Different areas require different lux levels. For example, a living room might need 100-200 lux, while an office might need 300-500 lux.
Calculate Lumens: Use the formula:
\[ \text{Lumens} = \text{Lux} \times \text{Area} \]

For example, if you have a 20 square meter room that requires 150 lux, the calculation would be:

\[ \text{Lumens} = 150 \, \text{lux} \times 20 \, \text{m}^2 = 3000 \, \text{lumens} \]

How to Calculate Lumens from Lux

Calculating lumens from lux is essential for determining the total light output needed for a specific area. Lumens measure the total quantity of visible light emitted by a source, while lux measures the illuminance or light intensity on a surface.

Steps to Calculate Lumens from Lux

Measure the Area: Determine the area over which the light is spread. This is usually measured in square meters (m²).
Determine the Lux: Lux is a measure of illuminance, or how much light is hitting a surface. This value is usually provided by the lighting manufacturer or can be measured using a lux meter.
Calculate Lumens: Use the formula:
\[ \text{Lumens} = \text{Lux} \times \text{Area} \]

For example, if you have a room that is 10 square meters and the illuminance is 150 lux, the calculation would be:

\[ \text{Lumens} = 150 \, \text{lux} \times 10 \, \text{m}^2 = 1500 \, \text{lumens} \]

How to calculate Candela from Lumens

Let's assume the following values:

Lumens = 1000 lm
Apex Angle = 30 degrees

Using the formula:

\[ cd = \frac{1000}{2 \pi (1 - \cos(30 / 2))} \]

Evaluating:

\[ cd = \frac{1000}{2 \pi (1 - \cos(15))} \]

The Candela is approximately 136.6225 cd.

How to Calculate Lumen To Watt?

The formula to calculate Watts (\(W\)) from Lumens (\(lm\)) is:

\[ W = \frac{lm}{lm/W} \]

Where:

\(W\) is the power in watts.
\(lm\) is the luminous flux in lumens.
\(lm/W\) is the luminous efficacy in lumens per watt.

How to Calculate LUX To Footcandles?

The formula to calculate Footcandles (\(fc\)) from Lux (\(lx\)) is:

\[ fc = \frac{lx}{10.76391} \]

Where:

\(fc\) is the illuminance in footcandles.
\(lx\) is the illuminance in lux.
10.76391 is the conversion factor from square meters to square feet.

How to Calculate Lux to Watt?

The formula to calculate Watts (\(W\)) from Lux (\(lx\)) is:

\[ W = \frac{lx}{lm/W} \]

Where:

\(W\) is the power in watts.
\(lx\) is the illuminance in lux.
\(lm/W\) is the luminous efficacy in lumens per watt.

Units of Light

Unit	Symbol	Description
Lumen	lm	Measures the total amount of visible light emitted by a source.
Foot-Candle	fc	Measures the amount of light received on a surface per square foot.
Lux	lx	Measures the amount of light received on a surface per square meter.
Candela	cd	Measures the luminous intensity in a specific direction.
Luminous Efficacy	lm/W	Measures the efficiency of a light source in converting electrical power to visible light.

Lumens vs Lux Frequently Asked Questions

What is Lumens (lm)?

Answer: Lumens (lm) are a measure of the total amount of visible light emitted by a light source in all directions. It indicates the brightness or luminous flux of the light, regardless of how it is distributed.

What is Lux (lx)?

Answer: Lux (lx) is a measure of the amount of light received by a surface, specifically the illumination or luminous intensity per unit area. It is a measure of the brightness of a particular area or space, taking into account the distribution of light.

How are Lumens and Lux Related?

Answer: Lumens and Lux are related in that both measure aspects of light, but they do so in different ways. Lumens measure the total light output of a source, while Lux measures the brightness of a specific area illuminated by that source. The relationship between them depends on the size of the illuminated area and the distribution of light.

Why are Lumens and Lux Important?

Answer: Understanding Lumens and Lux is crucial in lighting design because it allows designers to determine the appropriate level of illumination for a space based on its intended use. Lumens help in selecting the right light source, while Lux ensures that the space is adequately lit for visibility, comfort, and energy efficiency.