Light Bulb Types: A Guide To Understand The Shapes, Sizes, And Codes

Understanding the lighting terminology can be challenging if you are not from the industry. But knowing the language helps when looking to buy lights for yourself or your loved ones. Imagine going to a store and getting lost amongst the number of codes. I am sure nobody would prefer that! 

Recently one of my friends who moved to Michigan from India went bonkers with codes like A19, E26, C15, etc., and ended up calling me to ask, ‘what is an E26 bulb?’ Upon helping him, I realized the need for literature on this topic. Though I wrote an article mentioning everything about an E26 bulb, I also realized that there is so much more about the light bulb types that laymen might not know but will require to have knowledge.

Basic knowledge about light bulb dimensions, shapes, and codes is important whether you are replacing your existing lights or installing lights in a new setup. A light bulb’s primary and most essential characteristics are represented by a code that includes a letter (or letters) and a number. Knowing the light bulb shape codes, it gets more accessible for the user to understand whether the bulb meets their needs.

In this article, I will walk you through the different types of light bulbs based on their size and shape. After reading the article, you will get familiar with different codes of light bulbs and be able to identify the characteristics of a light bulb from its code. But before diving deep into the topic, let us understand what the light bulb shape codes represent.

What Do The Light Bulb Shape Codes Represent?

The markets are flooded with various bulbs, and it is tricky for the buyers to keep track of them. Thankfully each lightbulb has a code that tells you everything you need to know about the bulb. However, the codes are of no use until you can decipher them. 

The code for the light bulbs has two parts- 

• The letter part and 
• The number part

The letter part gives you information about the shape and the bulb type, and the number part depicts one-eighth of the bulb’s diameter at the widest portion in inches. For example, code A19 depicts that the shape of the bulb is arbitrary, and the diameter of the maximum width is one-eighth of 19 inches i.e., 2.4 inches. 

But do all codes represent the shape and size of the bulb? Well, no! Some codes represent the size and type of the bulb base. For example, E26 is the code for an Edison screw-type bulb base with a base diameter of 26 millimeters.

Light Bulb Shapes

When we talk about a light bulb, most people picture a pear-shaped bulb we have seen in our homes since childhood. Yes, the same bulb that you see in the WhatsApp emoji list.

But as we all know, these bulbs are not the only kind available on the market. These pear-shaped bulbs are Arbitrary Bulbs or Type A bulbs. Numerous other kinds of bulbs are available in the market in different shapes and sizes.

Obviously, the bulb’s variety in shapes and sizes is not only confusing but also overwhelming. Hence, the light bulbs have codes that help the buyer to learn about their several parameters.  These codes are in the form of a letter or letters followed by a number. 

The codes are not only restricted to the bulb shape and size. You can fix the modern lights into several kinds of fixtures. Hence, the base of the bulbs is also represented by codes giving you basic information about which bulb will fit in which sort of fixture. 

This section of the article will learn about some types of light bulbs and their codes. But before that, let us look at the light bulb size chart that will give you a glance at how varied the light bulbs are.

Type A Bulbs

Type A bulbs or the Arbitrary Bulbs are the classic household bulbs that resemble an inverted letter A. These are the traditional pear-shaped bulbs that we have seen in our homes since childhood. These bulbs are suitable for a variety of installations, such as lamps, ceiling lights, vanity lights, kitchen lights, closet lights, etc. Furthermore, the A-type bulbs come in a number of lighting technologies like incandescent lights, CFL, LED, High-Pressure Sodium, etc. 

Following are a few examples of A-type bulbs. The numbers in the codes refer to one-eighth of the diameter of the widest part of the bulb in inches. 

A15 bulb: A-type bulb with a diameter of 1.9 inches
A19 bulb: A-type bulb with a diameter of 2.4 inches
A21 bulb: A-type bulb with a diameter of 2.6 inches
A25 bulb: A-type bulb with a diameter of 3.1 inches

Type A bulbs are used in residential and commercial applications and have an Edison screw base. The most common of these bulbs are A19 bulbs, the most standard bulbs used in lamps. A15 bulb is also a popular one and is used in appliances

Type B Bulbs

Type B light bulbs are another common type of light bulb where B stands for the blunt tip. These lights resemble the shape of a blunt bullet. Some Type B bulbs bulge at the bottom and get thinner as they reach the tip, while others retain the narrow shape from bottom to top. 

Type B light bulbs are candle-like and popularly used in decorative light fixtures. These bulbs are commonly referred to as Candelabra bulbs for their decorative application. The Type B light bulbs carry less wattage than other bulbs and are often not the primary source of light in the room. 

Some of the type-B bulbs are as follows: 

B8 Bulb:  B-type bulb with a diameter of 1 inch
B10 Bulb:  B-type bulb with a diameter of 1.3 inches
B11 Bulb:  B-type bulb with a diameter of 1.4 inches
B13 Bulb:  B-type bulb with a diameter of 1.6 inches

The most popular bulb from this series is the B10 bulb. Furthermore, these bulbs are available in CFL, HID, incandescent, LED, etc., technologies, making room for everyone to choose as per their needs. 

Type C Bulbs

Type C bulbs, also known as Conical Bulbs, are shaped like cones or candle flame. Their shape may appear similar to the type-B or blunt-tip bulbs but they have a more distinct bullet shape with a point at the end. However, type-C light bulbs are also used for decoration like type-B light bulbs. You can use these light bulbs in chandeliers, pendant lights, night lights, club lights, and other decorative lighting applications.

Like type-B bulbs, type-C bulbs are also referred to as Candelabra bulbs for their decorative application and carry less wattage than other bulbs. Hence, these light bulbs are often not the primary source of light in the room. Also, these bulbs, too, are available in CFL, HID, incandescent, LED, etc., technologies, giving the buyers the liberty to choose what works the best for them.

Given below are some of the type-C light bulbs and their specifications.

C7 Bulb:  C-type bulb with a diameter of 0.9 inch
C9 Bulb:  C-type bulb with a diameter of 1.1 inches
C15 Bulb:  C-type bulb with a diameter of 1.9 inches

There is a CA-type bulb which is a special type of conical bulb with an angular tip at the top. The Conical angular bulbs or CA-type bulbs are shaped like a cone but their tip is bent at an angle.

Type F Bulbs

As given in the light bulb size chart, there are several light bulb types with a candle flame-like shape. Hence, mentioning candle flame bulbs many times can leave you confused. But if you read and observe carefully, all these types have slight variations in their shapes and hence, have different codes. 

Like the C-type light bulbs have a regular candle flame-like shape, E-type light bulbs have an extended candle flame-like shape, and the F-type bulbs have a flambeau-like shape. The Flame-tip or Flambeau light bulbs look like candle flames but have irregular grooves on the surface. Their unique shape provides them with an aesthetically pleasing look and lighting effect. F-type light bulbs are popular in hotels and restaurants but are often installed in homes too.

The various F-type light bulb sizes available for various lighting projects are as given below.

F10: F-type bulb with a diameter of 1.2 inches
F15: F-type bulb with a diameter of 1.9 inches
F20: F-type bulb with a diameter of 2.3 inches

Like other light bulbs, type F light bulbs, too, are available in various lighting technologies but the incandescent ones are popular for their vintage aesthetics.

Type L Bulbs

Type L light bulbs are long and tubular and are also known as linear lights. The most common linear lights are the LED tube lights we use at home. These lights are suitable for both indoor and outdoor use and can be found in different powers and sizes. You can buy the linear type light in LED, CFL, HID, and incandescent lighting technology.

The codes and dimensions of type L light bulbs are as follows.

L4: L-type bulb with a diameter of 0.5 inches
L5: L-type bulb with a diameter of  0.6 inches
L8: L-type bulb with a diameter of 1 inch
L12: L-type bulb with a diameter of 1.25 inches

Type G Bulbs

Type G light bulbs are easy to identify and distinguish because of their unique but simple shape. These bulbs feature a spherical round shape and hence, are also called the Globe lights. 

The type G bulbs are the ones that we usually see on the vanity lighting. A common installation of these bulbs can be seen around the mirrors. Basically, they work great in places where you would prefer ambient or bright lighting. Their impressive lighting ability makes them a great choice of light bulb for your house if you have an eye for statement designs.

It is easy to find the G-type light bulbs in Incandescent, CFL, HID, and LED lighting technologies.

Type-G light bulbs are available in several size variations. Some of these variations are as follows.

G16: G-type bulb with a diameter of 2 inches
G30: G-type bulb with a diameter of 3.8 inches
G90: G-type bulb with a diameter of 11.3 inches
G125: G-type bulb with a diameter of 16.6 inches

Type PS Bulbs

The type-PS lights may look similar to type-A lights, but there is a sweet difference. Pear Straight Lights or type PS light bulbs have a more rounded body than type A light bulbs. Due to the similarity in the pear shape with type-A bulbs, these are sometimes also referred to as the elongated standard bulb. However, these light bulbs are not the standard bulbs for the home, and I do not recommend using them in the place of A-series bulbs as the light bulbs are high wattage light bulbs not suitable for homes..

The typical type-PS light bulbs that are easily found are PS30 and PS40. The light bulb dimensions of the same as follows.

PS30- PS-type bulb with a diameter of 3.8 inches
PS40- PS-type bulb with a diameter of 5 inches

Utilitywise, PS30 light bulbs are popular in offices and retail stores, and PS40 light bulbs are popular for installation in radio towers, cellular towers, high tension wires, etc.

Type R Bulbs

Type-R bulbs or reflector bulbs come installed with an inbuilt reflecting surface. The reflector design of these light bulbs directs the light output towards the front instead of scattering the light all around. These light bulbs are suitable for installation in dining areas of homes and restaurants, in recessed cans, hotels, etc. If you wish to install these lights in your space, you can choose from incandescent lights, LED, or CFL.

The most common type-R light is R20. A few of the various reflector light bulb sizes are as follows.

R4: R-type bulb with a diameter of 0.5 inches
R12: R-type bulb with a diameter of 1.5 inches
R20: R-type bulb with a diameter of 2.5 inches
R30: R-type bulb with a diameter of 3.8 inches

Type T Bulbs

Type-T bulbs are another popular bulbs that can be commonly found installed in our surroundings. These are also known as Tubular Light bulbs due to their tube-like shape and come in various lengths and widths. Depending on their length, you can use type-T light bulbs in applications ranging from street lighting, chandeliers, floodlighting, departmental stores, etc., where a high light output and increased efficiency are essential. These lights are excellent at illuminating bright light for very little energy and are long-lasting.

No doubt, the T-type light bulbs are more functional than the decorative lights available. Like most other lights, these lights are also available in incandescent, CFL, HID, and LED technologies. The various tubular light bulb sizes are T3, T4, T41/2, T5, T51/2, T6, T61/2, T7, T71/2, T8, T9, T10, T14, and T20. 

The dimensions of a few of the above are mentioned below.

T3: T-type bulb with a diameter of 0.4 inches
T5: T-type bulb with a diameter of 0.6 inches
T8: T-type bulb with a diameter of 1 inch
T14: T-type bulb with a diameter of 1.8 inches

It is noteworthy that the L type light bulbs are not the same as the T type light bulbs as the former are linear in shape but the latter are tubular.

European Sizes For Light Bulbs

In Europe, the measurement of light bulbs is done in millimeters rather than in one-eighth of an inch. So, the letter in the code will represent the shape of the bulb and the number part represents the diameter of the widest part of the light bulb in millimeters. 

Hence, A19 light bulbs in Europe will be A60 
G30 light bulbs in Europe will be G95
R4 light bulbs in Europe will be R12
T10 light bulbs in Europe will be T32

Is There A Standard Light Bulb?

When you close your eyes and picture a bulb in your head, I am sure you see a medium-sized pear-shaped bulb. Yes, the same bulb that you see in the emoji section of your Whatsapp. This pear-like shape of the bulb that you pictured in your head has been in use since the day when Thomas Elva Edison invented light bulbs. Basically, what you envision is an A19 bulb. 

A19 is the standard bulb that most Americans have used in their homes for ages. The code A19 is used to represent the overall shape and size of a light bulb. The code has been in use since the era of incandescent light bulbs and now LED, HID, and CFL light bulbs continue to use the same code.

This size of the bulb is also the standard light bulb size.

The bulb is a standard bulb not only in the US but across the world. In the US and a few other countries like Japan, Canada, Taiwan, etc. with the standard voltage of 120V, the A19 light bulb is attached to the E26 base.

FAQs

Q1. What is the standard light bulb size?

Answer – The standard light bulb size is A19 in the US and A60 in Europe. It is a pear-shaped bulb with a diameter of 2.4 inches or 60 millimeters. 

Q2. Can an A19 light bulb fit into the fixture for the A21 light bulb?

Answer – Yes, an A19 light bulb can fit into the fixture for the A19 light bulb because the A19 light bulbs are smaller in all dimensions than the A21 light bulbs. Hence, they will fit into the fixtures and lamp holders designed for A21 lamps. Since they utilize the same E26 base, the A19 lamps will fit perfectly into the socket.

Q3. What is the difference between a type B light bulb and a type C light bulb?

Answer – Both type B and type C light bulbs are known as Conical Bulbs as they are shaped like cones. Their shapes may appear similar but distinct. The type B  are conical with blunt tip bulbs but type C light bulbs are bullet shaped with a point at the end. However, type-C light bulbs are also used for decoration like type-B light bulbs.

Q4. What type of light bulb should be installed on a mirror or in a vanity van?

Answer – Type G or globe-type light bulbs are best suited for mirrors and vanities as they work great in places where you would prefer ambient or bright lighting. Their impressive lighting ability makes them a great choice of light bulb for your house if you need bright light.

Q5. Which type of light bulb is used on radio or cellular towers?

Answer – PS40 light bulbs are the most common light bulbs used on radio or cellular towers.

Conclusion

Buying light bulbs can be a tedious task if you start reading their codes. The letters and numbers printed on the light bulbs are of no use unless you can decipher them. There are zillions of light bulbs available on the market and some of them have specific usage. If you know what the codes on light bulbs represent, selecting the light that suits your needs will become a lot easier for you. 

I hope this article will help you understand the meaning of the letters and numbers associated with a light bulb and enable you to understand the size, shape, and type of the light bulb.

If you have any other questions related to the light bulbs, write to me in the comment section.