What is the difference between E40 and E39 base?

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Have you ever stumbled upon a situation where you tried fitting a bulb into a fixture, only to realize it won’t fit perfectly? That’s probably because the bulb base and the fixture socket didn’t match. The tiniest difference can lead to a mismatch. Today, let’s dive into the difference between E40 and E39 lamp bases.

E40 and E39 are not the same. While they might seem indistinguishable at a casual glance, there are subtle differences that make them unique. These slight variations, though seemingly minute, can make all the difference when it comes to proper fitting and performance.

Being in the industry, we at James Lighting know how crucial such details are. This knowledge empowers both manufacturers and consumers.

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What are E40 and E39 bases?

Firstly, when we talk about E40 and E39, we’re referring to specific base types for light bulbs. They indicate the type of screw base a bulb possesses.

In our experience at James Lighting, we’ve found that while many customers are aware of the basic design, they often get confused about the specific dimensions. Let’s clarify that.

How do the dimensions vary?

The E40 base has a diameter of 40mm. It’s predominantly used in Europe and parts of Asia. On the other hand, the E39 base, commonly known as the Mogul base in North America, has a diameter of 39mm.

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Yes, it’s a difference of just 1mm. But in the world of lighting, especially in manufacturing, precision matters. At James Lighting, we ensure the precision of our lamp holders to provide seamless fitting.

Where are they commonly used?

E40 bases are more commonly found in Europe and some parts of Asia. They are often utilized in larger lighting applications, such as street lights, high bay lights, and other industrial settings.

On the flip side, the E39 lamp sockets, being popular in North America, find their applications in similar settings. Though the regions might differ, their applications remain quite consistent.

Compatibility issues?

Ever tried fitting an E40 bulb into an E39 socket or vice versa? Though it may seem feasible, it’s not recommended.

Trying to force fit can lead to improper connections, leading to potential safety hazards. As a manufacturer, we’ve encountered such instances, and we can’t stress the importance of using the right fit enough.

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Compatibility doesn’t end at fitting alone. Electrical parameters, material compatibility, and temperature tolerance also play crucial roles. All these elements need to align for the optimal and safe functioning of the lighting solution.

Conversion: Is it possible?

Fortunately, there are adapters available that allow one to use an E40 bulb in an E39 fixture and vice versa. These are handy for those who have fixtures from different regions or for manufacturers like us, who cater to a global audience.

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However, while these adapters provide a solution, they may not always be the most efficient or safe route. It’s crucial to ensure that any adapter used is of high quality, and the combined length of the adapter and bulb doesn’t interfere with the fixture’s design.

Why the distinction?

Why have two standards that are so close in design? Historical, regional, and manufacturing differences led to these standards. Each standard evolved to cater to specific regional requirements and electrical standards.

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At James Lighting, understanding these nuances aids us in crafting the perfect lamp holders. It’s not just about creating a product; it’s about creating the right product for the right audience.


The difference between E40 and E39 might seem trivial, but as highlighted, this tiny distinction can make or break the efficiency and safety of a lighting solution. Whether you’re a manufacturer, distributor, or end-user, understanding these differences ensures safer and more efficient lighting experiences.

In the ever-evolving world of lighting, being knowledgeable is the key. At James Lighting, we pride ourselves on our expertise and our commitment to illuminating the world with precision and quality.

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