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Are B11 And E12 Bulbs Interchangeable?

How many home projects have you seen on YouTube and thought to yourself: well, that’s easy enough! And you get cracking on it, ready with your measurements, your written plan, and all the equipment you need to shop for.

But sometimes, you hit a glitch that has you scratching your head in bewilderment as to what has gone wrong.

One such scenario is the common mixup and confusion when choosing candle-shaped bulbs. It is usually assumed that E12 and B11 are two basic types of the bulb, and one has to choose between the two options.

However, while in the market, you can find one bulb that has both E12 and B11 in its description. How come?

The codes E12 and B11 refer to two different specifications. E12 is the type of the bulb’s base, while B11 refers to the bulb type and describes its shape. Both of these are usually found in the same bulb, leading to the mixup.

E12 And B11 Codes Explained

E12 bulbs B11 and CA11

There is widespread confusion when choosing candelabra bulbs for chandeliers, string lights, signage, or marquees. You need a very specific base for the bulbs to fit in your socket.

When people need to buy these bulbs, the codes E12 and B11 cause doubt about which of the two codes applies to their specific requirements.

The reality is that both of these codes refer to entirely different things and are not mutually exclusive.

E12 is the description of the base type of the bulb and is the candelabra Edison screw base.

B11 is the description of the bulb type and the candle shape of the glass body. The letter refers to the shape of the bulb, while the number refers to the diameter.

The confusion usually arises because these two codes and descriptions are usually found in the SAME bulb, where one refers to the base and the other refers to the bulb.

Diameter Specification

As if buying the right bulb was not puzzling enough, that there needed to be multiple codes looking similar but referring to different specifications.

Have faith because these codes are there to help you pick the EXACT bulb that would fit your needs. I will help explain the difference.

Going into detail, the E12 on the bulb code means an ‘Edison’ screw-in type with a base that measures 12 millimeters across the widest part of the base (not bulb).

For candle flame chandelier bulbs, most base types are E Edison, although another common screw base is E26, measuring 26mm.

On the other hand, B11 means the bulb’s glass body ends in a ‘Blunt’ tip at the top, usually shaped like a candle, bullet, or torpedo!

In standard American units, the measurement is given in eighths of an inch. So the number 11 refers to the diameter, but it becomes 11/8, so 1.375 inches.

This is even more confusing since the diameter of the bulbs is given in inches. In contrast, the diameter of the base types is given in millimeters!

When converted to mm, a B11 is about 35 mm in the widest part of the glass body. The diameter of a bulb is always taken at the widest part, as that’s the size that matters when it comes to light fixtures.

On the other hand, an E12 is, as we know, 12 mm in diameter, but unlike the shape, the base is not converted to eighths, so it just stays as 12 mm.

The E12 helps you decide which bulb base will fit into the light socket that your fixture has, and after that, the B11 will help you pick out the desired shape of your bulb.

Determining the required shape of the bulbs is also quite important. Sometimes a light fixture cannot allow a bigger bulb or a globular bulb to fit in, so only the slim bullet pendant lights will serve the purpose.

In other cases, it is all about aesthetics. Traditional chandeliers and string lights look distinctively beautiful due to the bulbs’ candle shape that has been used for years.

So first comes the base, and then you can pick out the shape. If you don’t find the exact bulb with this combination, you can do one of two things.

First, if you have found the B11 shape, but they aren’t the E12 base types, you can purchase adapters (Amazon) to change the base from an E12 to an E26.

But this can be an expensive option if you need to buy adapters for every socket. If you’ve got many light fixtures to fill, it makes sense to buy the correct light bulbs.

Secondly, you can stick to the E12 screw base, but opt for a CA11 bulb type similar to the B11; and is also shaped like a candle but is quite pointy at the end, like a candle flame.

Other options can include a G50 bulb type, which is spherical and like a globe.

Both B11 and CA11 are 35 mm at their widest part of the body, so they can be easily interchanged.

In case you have not yet purchased the light fixture that your new bulbs will go into, you can use an E26 base with the traditional B11 bulb type, provided that the new fixture will be compatible with the E26 base.

Are B10 And B11 Bulbs Also Interchangeable?

chandelier with B10 bulbs

Because the “B” rating of a bulb relates to the bulb shape and not the size of the bulb base, they are interchangeable, providing you’re not installing them somewhere extremely snug.

The difference in width is 1/8th of an inch, so realistically I don’t think you’ll ever find any lighting fixtures that can’t fit either.

CA10 light bulbs are similar, too, although they have a bent tip instead of the blunt tip of a B light. They are more of a flame shape and are perfect for a chandelier since they look like a natural firelight.

Especially if you have a poor quality bulb that flickers! I’m joking of course, and if your LED lights are flickering then you should try to work out why and resolve it.

Here’s a quick guide to the different bulbs that are often used in the chandelier style:

Bulb type Diameter Tip shape
B11 1 3/8” Blunt
B10 1 1/4” Blunt
CA10 1 1/4” Bent

So yes, B10 and B11 (and CA10) bulbs are interchangeable as long as they all have the right fixture size to fit your wall sconces or candelabra base.

Where Are B11 E12 Bulbs Used?

E12 B11 bulbs are most commonly used in decorative lighting and festive settings, such as chandeliers, wall sconces, pendant lights, night lights, string lights, and numerous other applications.

That is why the E12 bulb base type is commonly referred to as candelabra. This is another confusing aspect as one thinks of the candle-like BULB SHAPE when imagining a candle shape. In this case, candelabra is the name of the BASE.

And that is exactly why this guide needed to be written!

Can You Use Other Shapes On E12 Base?

So at the end of the day, the bulb you need to purchase is restricted by the socket you already have in your light fixture.

Let’s suppose your fixture has a threaded socket that will take a screw-in bulb, then you need to look for the E12 base type, as nothing else will fit in the socket!

Once you have sorted all E12 base bulbs and can see a few different options for the BODY of the bulb, you can then choose the bulb type.

The bulb type can be labeled A for Arbitrary, the classic, pear-shaped light bulb shape used for general lighting in kitchen downlights.

Or the bulb type can be labeled G, which signifies the globe and is a very spherical, round-shaped bulb used for decorative purposes and brilliant lighting in vanities and bathrooms around mirrors.

Finally, you can find the B or C bulb types, which is most likely what you would have been looking for if you are in the market for the E12 base.

So the B11 bulb type is explicitly most often associated with E12 lamp bases, to such an extent that a candelabra bulb is also commonly referred to only as a ‘B11’.

Final Words

This has been an enlightening guide to write and, hopefully, for you to read as well.

Do you have light fixtures or decorative lamps and chandeliers that need the E12 B11 bulbs to look beautiful?

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Check out my free bulb picker and select the right bulb within few clicks.