Understanding Light Bulb Base Types: Screw Bases
Have you ever found yourself shopping for screw base light bulbs but with no clue as to what will fit your fixture? There are two things you must keep in mind. Firstly, you must know the base type of bulb you want to replace. If you are finding a bulb for a new fixture, you can find this out by checking the diameter of the lamp holder. Secondly, you must consider the size and shape of the bulb you want. Differently shaped bulbs are better suited for certain applications and stylistic designs. This article will address the first concern: how to distinguish the different screw base types.
How do you distinguish between light bulb base sizes?
Screw-bases are named after the inventor of the Edison screw socket: Thomas Edison. They’re defined by the letter E (Edison) followed by a number referring to the lamp holder width in millimeters. There are several types of screw bases, including E26, E27, E12, E14, E17, and E39. Each base type also has a descriptive term that denotes the thread size: medium or standard, intermediate, candelabra, and mogul.
After you know the screw base type you need, decide what shape and size of the bulb you want. LED bulbs are described with a letter or series of letters denoting the bulb series and a number referring to the diameter of the bulb in eighths of an inch. Understand the different light bulb shapes and sizes here.
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E26/E27 Medium – Edison 26-mm or 27-mm Diameter
Bulbs with E26/E27 bases are the most popular of all screw-base bulbs. E26 base bulbs are primarily used in North America, while E27 bulbs are more commonly used in Europe, Asia, Australia, and South America. Bulbs with these base types can be used interchangeably, although E26 and E27 sockets are rated for different voltages. E26 and E27 base bulbs are commonly used for general lighting in standard light fixtures, such as ceiling lights, lamps, can lights, outdoor spotlight and flood light fixtures, and vanity lights.
Common bulbs with E26/E27 bases:
A-shaped bulbs: A19, A15, A21
Globe-shaped bulbs: G30, G25, G16.5
PAR bulbs: PAR16, PAR20, PAR30, PAR38
BR bulbs: BR20, BR30, BR40
Blunt-tipped bulbs: BA11
Marquee and sign bulbs: S11, S14
ST bulbs: ST18, ST19, ST21
E12 Candelabra – Edison 12-mm Diameter
E12 bulbs, also known as Miniature Edison Screws (MES), have a 12mm diameter screw base. Many bulbs with these bases are designed to mimic the look of a candle flame. Bulbs with E12 bases are commonly used for decorative lighting applications, such as chandeliers, wall sconces, Christmas lights, restaurant pendant lights, ornamental lights, residential or commercial string lights, and night lights.
Common bulbs with E12 bases:
Small tube-shaped bulbs: T8, T6, T22
Candle-flame-shaped bulbs: C7, C9, CA10, B10
Small globe-shaped bulbs: G14, G16, G50
Blunt-tipped bulbs: B10, B11, BA11
E14 European – Edison 14-mm Diameter
E14 base bulbs are often referred to as Small Edison Screws (SES). They are popular in Europe and other markets for small light fixtures and spaces where a compact bulb is necessary. Popular applications for E14 screw base bulbs include chandeliers, wall sconces, lamps, Christmas lights, restaurant pendant lights, ornamental lights, residential or commercial string lights, sign and marquee lights, night lights, and bathroom vanities.
Common bulbs with E14 bases:
A-shaped bulbs: A15
Small tube-shaped bulbs: T8, T6, T22
Candle-flame-shaped bulbs: C7, C9, B10
Small globe-shaped bulbs: G14, G16, G50
Marquee and sign bulbs: S11
E17 Intermediate – Edison 17-mm Diameter
E17 intermediate base bulbs can be used for appliance lights, such as microwave lights, refrigerator lights, and range hood lights. They’re also found in ceiling fan light fixtures and desk lamps. Similar to E12 candelabra bulbs, bulbs with E17 bases are also used for decorative applications, such as chandeliers, wall sconces, Christmas lights, pendant lights, ornamental lights, and sign or marquee lights. These base types are not widely common in the US.
Common bulbs with E17 bases:
A-shaped bulbs: A15
Small tube-shaped bulbs: T8, T6.5, T22
Candle-flame-shaped bulbs: C7, C9
Small globe-shaped bulbs: G14, G16, G50
Marquee and sign bulbs: S11
E39/E40 Mogul – Edison 39-mm or 40-mm Diameter
E39/EX39 bases are primarily used in North America, while E40 bases are popular in Europe and other markets. EX39 base bulbs can operate in E39 and EX39 lamp holders since EX39s have a longer tip, but E39 base bulbs cannot operate in EX39 lamp holders. These powerful, energy-efficient bulbs have high light output and are used to replace HID bulbs in industrial fixtures, such as high-bay warehouse lights, parking lot lights, canopy lights, and wall packs. LED E39/EX39 base bulbs typically have a cylindrical shape like ED and BT HID bulbs. Another popular type of E39/EX39 screw base bulb is the LED corn bulb, which resembles a corn cob. E39 and E40 base bulbs can be used interchangeably, however, keep in mind that their respective sockets are rated for different voltages.
Common bulbs with E39/E40 bases:
PAR bulbs: PAR38
Blown tubular bulbs: BT37, BT56
Elliptical dome bulbs: ED17, ED28, ED37
