Whats The Difference Between All The Various Edison Screw Base Light Bulbs?

August 04, 2016 2 Comments

edison screw base light bulbs

Buyer: "Hey, I need a chandelier light bulb replacement for my pendant lamp."

Seller: "Okay, what is the voltage you need ??"

Buyer: "120 Volt, please."

Seller: "E12 or E14 fitting?"

Buyer: "errrrrrr"

Ever felt confused about fitting choices like the buyer above? You are not alone. Choosing the correct fitting can be a confusing and technical task. However, it's actually much simpler than you think.

To bring you into the light and out of the dark, here is our comprehensive guide for Edison screw fittings and its applications.

Introduction to Edison Screw

Invented by the infamous Thomas Alva Edison, most likely you've seen and used an Edison Screw before. It's that screw-like socket in the bottom of most light bulbs all around the world. According to Energy.gov's history of light bulbs, the Edison screw has been around since the late 1800s although it was only patented in 1909. The Edison screw has become the international standard of lighting sockets ever since.

This international standard socket for light bulbs allows uniformity in light bulb design all around the world and is used in over 80% of the light bulbs, with the rest being of other sockets like the bayonet caps,  and two-pin sockets for tubes among others.

The screw comes in various size from E5 to E40, with the number behind the E represents the diameter size in millimeters. This E5 to E40 size are then deemed fitting, and each size are applied for different types, and sizes of light bulbs.

For example, E10 (10 mm) is commonly utilized in decorative lamps you often saw on Christmas trees, and some vehicle headlights and tail lights, as well as indicator lights on devices.

Some fitting sizes are more commonly used with a wide array of applications, and we'll learn about each one of them. Let's begin with the E10:


The 10 millimeters Edison screw is also often called the Miniature Edison Screw (MES). Being so small, it's used in limited applications. But, arguably the E10 lamps could be the most widely distributed all around the world, because of its application in flashlights, one of the most used lighting appliances in the world.

Outside its applications in flashlights, it is also used in vehicles, bicycle lamps and indicator lamps on many devices such as vintage radios. They are also often used in some Christmas decorations.

Check out our  E10 bulb for many applications described above here.


11mm Diameter , Deemed the mini candelabra Edison screw (mini-can), its applications are very limited. The most obvious application is obviously for 120-volt chandelier/candelabra, but the E12 variant is more common (more on that later). Low voltage models are used on Lionel toy trains and other toys

It is also often used for ceiling fans,kitchen applications, photography use, and select machinery.

Need an E11 tungsten halogen replacement? We have just what you need here.


As the name suggests, the fitting is 12 millimeters in diameter size and is often deemed the Candelabra Edison Screw (CES). It is the home of C7-sized lamps, so if you bought a C7 lamp before, it utilized the E12 fitting.

As mentioned before, the E12 fitting is very commonly used for 120-volt candelabra/chandelier lamps usage. It is also often found in lightings for boats, as well as some Christmas and other decorative lamps.

Check out our collection of chandelier E12 lamps here.


The 14 millimeters Edison screw is also called the Small Edison Screw (SES), and the term "SES bulbs" is often used.

Its main applications are for 230-Volt bulbs, especially the smaller candelabra bulbs. So, if you live in Asia, Austraila, Europe, New Zealand, Africa, and most South American countries, most likely you've seen this fitting before.

Its application can vary widely and the bulbs can come in many shapes such as golf-ball shape, candle (chandelier) shape, pygmy shape, and traditional bulb (ball) shape.

If you live in a country with the 230-Volt voltage, most likely E14 is the standard socket for many of your smaller household bulbs. If you ever have an inflatable Santa Claus, the lamp also often use the E14 fitting. Need a replacement? See our collections of E14 bulbs here.


We come to the Intermediate Edison Screw (IES), and we come back to the 120-volt range. The 17 millimeters fitting is the standard for many 120-volt appliance lightings, such as those we often found in microwaves and ovens, sewing machines, refrigerators, and other small appliances.

Outside its usage in 120-volt appliances, it is also often utilized as room lightings in tight or hard-to-reach spaces.

Appliance lamps are often called C9 lamps, so if you're looking for fittings for C9s, you know what to look for.


The E26 and E27 are often interchangeable, and both are called (Medium) Edison Screw, so it's abbreviated MES or simply ES. Also often called the one-inch Edison Screw.

It is the standard for most light bulbs, with the E26 being the standard for 120-volt bulbs (American usage), and E27 being the standard for 230-volt countries. Their insignificant 1mm difference made the bulbs interchangeable, and E27 bulbs can fit E26 fittings and vice versa.

Being the standard for lighting usage, many low-voltage bulbs (12-volt,24-volt, etc.) are also designed to fit the E26/E27 fitting. Check out our collections for the standard Edison Screw bulbs.

Still unsure of which one to use in your country? Check out this complete list by WorldStandards to check your voltage.


The 39 or 40 millimeters fitting is commonly called the Goliath Edison Screw (GES).In the U.S., it is also often mentioned as Mogul Edison Screw, or simply Mogul.

Fittings above E26/E27 are fairly uncommon, but the E39 and E40 deemed a special mention because of its wide usage in industrial and farm applications.

Common applications include most warehouses, barns, factories and other industrial lightings with more than 250W in wattage.

As with E26 and E27, the E39 is commonly used in the U.S. for the 120-volt industrial lightings. On the other hand, the E40 is utilized for 230-volt lightings. Again, they are interchangeable with insignificant 1 mm difference.

A Throwback Edison Fitting.

Other Edison screw fittings are quite uncommon in applications; they are the E5, also called LES (Liliput Medium Screw), and the E29, deemed [Admedium] Edison Screw (ES).

They are fairly uncommon nowadays, although the E5 is still sometimes used as indicator lights for some devices, as well as some small (Christmas) decorative lamps.

Thats What Edison Codes Are All About

After we went through all the Edison Screw fittings, it's not so confusing anymore, is it? When you're confused about the fitting for your screw fitting bulb, simply measure the diameter of the screw fitting with a ruler.

When a ruler is not available, the most common fittings, the E26/E27, and E12/E14, is roughly the same length of an adult's thumb (the E26/E27) and little finger (the E14, the E12 is 2mm shorter.) You can also use this diagram by Home Depot to determine your socket.

Most of the time, you can recognize the fitting right away from its application. If your microwave bulb broke, most likely it belongs to the E17 family. On the other hand, if your bathroom's main bulb broke off, most likely its an E26 or E27 depending on your location.

Still haven't found what you're looking for? Or want to get more technical? Check out the complete listing of lamp sockets by International Electrotechnical Commission (PDF).

Now the Edison screw shouldn't be too intimidating!

2 Responses


August 03, 2020

I’m a retired mechanical engineer and a current Florida State Certified mechanical contractor qualified to sit for a number of other construction industry licenses chiefly the state certified electrical contractors license. I’ve got a number of high end mics and two Starrett dial calipers. Since both are in inches, I simply must convert to mm. My research thus far has shown me about Edison and the light bulb standards in naming practices. However, I’ve not yet found the threads per mm. Perhaps I’m not thinking about this correctly. There are very similar diameters at Home Depot but the threads per mm are different. I’ve taken the major diameter and added the minor diameter and then averaged to get a very precise diameter of 11 mm. The threads per mm are .394 tpmm. Does that sound reasonable for an E11 base?

J. J. Woods
J. J. Woods

December 31, 2017


I have a Christmas illuminaated Victorian village decoration which uses 12 volt 3 watt bulbs and they blow frequently. I expect that they will become more difficult to obtain in the future. Therefore I wonder if it is possible to get compatible LED bulbs utilising the transformer or, preferably, to remove the transformer completely. The supply is 240 volts 50 Hz. Using a vernier to measure the base of the bulbs I get a reading of 11.64 and therefore don’t know if I require E11 or E12 bulbs. I don’t know what the tolerance would be. Would the E12 be too tight in the fitting and, conversely, would the E11 be too loose.

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