Candlepower vs. Lumens
Understanding the difference between candlepower and lumens is essential when choosing the right type of light. This guide clarifies both terms and explains how to convert between them.
Although "candlepower" is still commonly used, the official term is Candela (cd), which replaced candlepower as the correct unit of measurement in 1948.
What's the Difference?
The main distinction comes down to what each term measures:
Candlepower (or Candela) measures luminous intensity-how bright a light is in a specific direction. It describes the brightness of a focused beam at its most intense point.
Lumens measure luminous flux-the total amount of visible light emitted by a light source in all directions.
A Simple Analogy:
Imagine a flashlight:
Candlepower (Candela) refers to the brightness of the central, concentrated spot in the flashlight beam.
Lumens tell you how much total light is being emitted from the flashlight, including both the central bright spot and the spill of light around it.
When to Use Each Term
Candela (Candlepower) is used for focused light sources like flashlights, spotlights, laser pointers, or car headlights. It indicates how powerful and far-reaching the beam is.
Lumens are typically used for ambient lighting, like ceiling lights, desk lamps, or bulbs. It tells you how much total light is being spread in a space.
Conversion Formula
Although they measure different things, you can approximate a conversion between the two using this formula for a uniform light source:
1 Candela (Candlepower) = 12.57 Lumens
This conversion assumes the light is being emitted evenly in all directions, which is often the case in theoretical calculations.
Practical Conversion Examples
Converting Candlepower to Lumens: Multiply the candela value by 12.57.
Example 1: A 10-candela flashlight has a light output of about 125.7 lumens (10 x 12.57).
Example 2: A 1 million candlepower spotlight produces approximately 12.57 million lumens (1,000,000 x 12.57).
Converting Lumens to Candlepower: Divide the lumen value by 12.57.
Example: A light bulb emitting 600 lumens has an intensity of about 48 candela (600 ÷ 12.57).
Important Note: This conversion is an approximation. In reality, the actual intensity (candela) of a light with a given lumen output depends on how the light is shaped and directed by reflectors and optics.
Frequently Asked Questions
Which is brighter: lumens or candlepower?
The two terms measure different types of brightness. A high-lumen bulb will light up an entire room, while a high-candlepower spotlight will project a concentrated beam over a long distance. You can't directly compare them, as they serve different purposes.
What's the difference between Candela and Lumens?
Candela measures the intensity of light in one direction (like a spotlight).
Lumens measure the total light output in all directions (like a regular light bulb).
How many lumens is 3 million candlepower?
Multiply 3,000,000 by 12.57, and you get approximately 37.71 million lumens.
Conclusion
In summary:
Use Lumens when you want to know how much total light a fixture will produce to brighten up a space.
Use Candlepower (Candela) when you need to understand how intense and far-reaching a focused beam of light is.
Knowing the difference will help you choose the right lighting for any need, from cozy indoor lighting to powerful outdoor spotlights.
