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 Light bulbs come in all kinds of shapes, sizes, and types. Knowing what size, type, and shape you need for a given application can be difficult, especially when you are not familiar with the sizing chart for the light bulb bases. Light bulb base size is crucially important to ensure a given lightbulb will fit into its designated socket. When shopping for a light fixture or lightbulb, it is important to keep the socket and base size in mind. 

Below is a breakdown of the most common light bulb base sizes as well as ways in which you can determine the size base of any given light bulb or light socket. By being equipped with the knowledge of bulb, socket, and base sizing, you can ensure you're getting the correct light bulb you need, saving you the headache of having to return something because it was the wrong size. This is increasingly important when buying bulbs online because it can cost you money to simply return the bulb due to a sizing error on your part. 

Being knowledgeable about sizing and double-checking the size before ordering can save you the hassle and money involved with processing a return or restocking fee. 

Determining Base Type

Light bulbs have a wide variety of utilizations that each take on different needs such as space, security, and ruggedness. Each of these different needs can be accomplished by the way in which they connect to the socket and their type of connector. 

In general, the most utilized connections include 2 pin connections, a screw base, a festoon base, or a bayonet style base. These connectors have different sizes, but each category acts in a similar manner regardless of size. 

Typically festoon and bayonet bulb bases are utilized in automotive lighting because they are able to securely fasten relatively small bulbs into place and keep them in place even with the vibrations experienced during normal driving. 2 pin connectors are widely used for light bars found in workspaces, hospitals, and closets with fluorescent bulbs. 

While 2 pin fixtures are utilized, replacing them with LED light bars is a great way to decrease operation costs and increase the longevity of the lights. 

The standard and most common light socket type is the screw type connector. This style connector has been around since Thomas Edison created it and has largely been kept the same over a hundred years later. This bulb base consists of a corkscrew groove in the base that is able to screw into its designated socket securely and easily. Since the attachment is in a screw-like fashion, there is no chance that an individual can accidentally reverse the polarity of the bulb and break it. ?


Once you have determined the base you have, you are one step closer to understanding what base light bulb you need. The other aspect of getting the correct bulb is determining the size of the connector. 

Each connector type described above comes in a variety of different sizes to fit different applications. The connectors themselves come in different sizes, but the bulb shape also comes in many different sizes. 

When looking at sizing, both the bulb sizing and connector sizing need to be taken into account. 

For bulb sizing, there are two components to the size designation. There is a letter followed by a number. The letter designates the bulb's shape while the number represents the diameter at the widest point of the bulb's shape. For example the light bulb size of A-19 is a standard light bulb shape with a diameter of 19. The bulb shape is important to know because it could mean the difference between a bulb fitting into a housing or not. 

Edison screw type connectors are the most widely utilized in lighting fixtures and are the easiest to get wrong with sizing. The screw bases all look the same and only vary in the diameter that they are. The standard light bulb base type is the screw type and has a diameter of 26 millimeters to 27 millimeters. These size connectors are given the name E26 and E27 respectively because they are edison screw connections with a diameter of 26 and 27 millimeters. 

Sockets for either one are compatible since there is a low difference in the two. This means that if you have a 27 millimeter socket, you should be able to fit a 26 millimeter bulb without issue. Anything below or above the standard is utilized for specialty lighting. 

Below the standard size are mainly E11 and E12. These sizes are also called candelabra lights because they are mainly used in decorative fixtures to resemble a candle. For the larger than standard sizing there is the E39 and E40. These lights are typically used with higher wattage bulbs and are not common for home use.

Picking the Right Bulb

With sizing and connector type all figured out, it comes time to determine the type of light you want. There are many types to choose from but the best and most efficient type of light you should get is an LED light. 

LEDs come in virtually all bulb and connector sizes and can offer more efficiency, brightness, longevity, and functionality. LED light bulbs can even have added functionality like motion detection, which allows you only to have light in a room when you're in it and need the visibility. 

Final Thoughts

Overall, buying a light bulb is no longer as simple as it once was. With so many different needs for light bulbs and so many different kinds of connectors, it is very easy to get confused and accidentally get the wrong size bulb. 

By being educated on bulb sizes, connector types, and connector sizes ahead of time will ensure you will never have to go through the hassle of returning an item that wasn't able to fit. By assessing the type of bulb you need on your own you can even enjoy the luxury of having light bulbs sent directly to your door all from the comfort and safety of your home.




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