Light Bulb & Socket Guide: Info on Sizes, Types & Shapes (2024)

PartyLights.com hopes to take the guessing game out of decorative string light shopping. There are several light bulb base sizes and shapes. We've provided this light bulb and socket guide to help you understand the industry terms and help you with bulb identification.

Light Bulb Base Identification

There are many light bulb base sizes available. PartyLights.com carries the three most common base sizes used in decorative string lights. On our website, we refer to our bulbs and string lights as C7, C9, and Medium. The industry uses many terms for the same size:

The following provides dimensions of a bulb socket which is helpful if you're trying to match the socket size of a bulb you already have.

Light Bulb & Socket Guide: Info on Sizes, Types & Shapes (1)

A further explanation of the light bulb base sizes, you can look at the letter-number references (E12, E17, and E26) to help understand a bulbs base style and size. The first letter designates the shape or form of the base, and the number represents the width of the base (normally in millimeters). For example, our 11S14 bulb has an E26 base — the "E" refers to the style which is an Edison screw-in, and the 26 means it has a 26 mm base width.

Light Bulb Shapes

Similar to identifying a base size, light bulbs use a letter-number reference to reflect the shape and size of a light bulb. The letter refers to the shape, and the number refers to the size*. Here's a list of the letters used for bulbs we carry and their meaning:

  • A (Arbitrary) ... Most closely resembles a standard household bulb.
  • C (Conic) ... Often referred to as like a traditional Christmas tree bulb.
  • G (Globe) ... Round or circular shape.
  • S (Sign) ... Sometimes called straight-sided, they were traditionally used in signs.
  • ST (Straight Tapered) ... This shape is most often seen in vintage, Edison-style bulbs.
  • T (Tubular) ... A tall narrow tube-shape often used in vintage, Edison-style bulbs.

Below shows the bulb styles available at PartyLights.com for our decorative string lights:

Light Bulb & Socket Guide: Info on Sizes, Types & Shapes (2)

*The size of the globe part of a light bulb varies with decorative lighting. Most bulbs are measured in eighths of an inch, however decorative lighting globe-shaped (or G) bulbs are measured in millimeters. For example, an S14 would be a sign bulb shape and 14/8" (or 1.75") and our decorative lighting G40 bulbs are globe shape and 40 mm (or approximately 1.5"). Alternatively, a purchased brand (e.g., GE or Sylvania) of a non-decorative lighting, standard household bulb may have a G40 bulb that is 40/8" in size (or 5"). An industry confusion for sure, so for accurate sizing of our decorative string light bulbs, be sure to refer to each item's product specs.

Bulb Comparison

The image below compares our three C7 (E12) base bulb sizes: G30, G40 and G50.

Light Bulb & Socket Guide: Info on Sizes, Types & Shapes (3)

The image below compares our G40 and G50 bulbs in C7 and C9 base sizes.

Light Bulb & Socket Guide: Info on Sizes, Types & Shapes (4)

The image below compares our G50 bulbs in all three base sizes.

Light Bulb & Socket Guide: Info on Sizes, Types & Shapes (5)

Bulb Shopping

All three bulb socket sizes are available at PartyLights.com — C7/E12/Candelabra base, C9/E17/Intermediate base and Medium/E26 base.

Light Bulb & Socket Guide: Info on Sizes, Types & Shapes (2024)

FAQs

Light Bulb & Socket Guide: Info on Sizes, Types & Shapes? ›

The light bulb codes are represented by a letter or a series of letters with a number. Take A21 for example, letter 'A' indicates standard household incandescent shape, and '21' indicates a diameter of 21 divided by 8 inches, or approximately 2.6 inches. There are a variety of light bulb bases sizes also.

What are the different size light bulb sockets? ›

Edison Light Socket Sizes Chart
SizeNameBase major diameter (thread external)
E12Candelabra Edison Screw (CES)12 mm
E14Small Edison Screw (SES)14 mm
E17Intermediate Edison Screw (IES)17 mm
E26Edison Screw (ES or MES)26 mm
7 more rows
Nov 16, 2021

What are light bulb shape codes? ›

8+ Light Bulb Shapes and Code Meanings
CodeShape
ATeardrop/bulb
BBullet
BRBulged reflector
BTBulged tube/chimney/blunt tip/bent tip
8 more rows
Jun 29, 2022

How do I know what shape my light bulb is? ›

The light bulb codes are represented by a letter or a series of letters with a number. Take A21 for example, letter 'A' indicates standard household incandescent shape, and '21' indicates a diameter of 21 divided by 8 inches, or approximately 2.6 inches. There are a variety of light bulb bases sizes also.

How do I know what size my light socket is? ›

Light bulb base measurements will be labelled using a code similar to the one used for the bulb. For example, a standard light bulb base is an E27, which means that the base is an Edison screw base that measures 27mm. Screw and bayonet bases are measured right across the bottom.

What is the difference between E26 and A19? ›

A19 is the shape and diameter of the bulb, while E26 refers to the screw type (Edison) and the base diameter. An E26 light bulb is a standard size that can be used in many different fixtures, while an A19 is a specific shape and size bulb that fits into certain fixtures (like track lighting).

What does E26 mean on a light bulb? ›

The letter "E" in E26 refers to Edison Screw, the most standard of lamp bases, while the numerical "26" refers to its diameter in millimeters (approximately 1 inch). E26 is also commonly referred to as a Medium Edison Screw (MES).

What does E12 bulb mean? ›

E12 uses the same naming system as E26, whereby the letter "E" signifies an Edison screw base. The two digits after the letter "E" indicates the diameter of the screw base, in millimeters - 12 millimeters, or approximately half an inch.

Does bulb shape code matter? ›

For each of these types, the bulb light is produced by a different process. Light bulbs can also be distinguished by shape and base design. These differences do matter, as certain types of bulbs are recommended for certain types of fixtures.

Do light bulb shapes matter? ›

Pay Attention to a Light Bulbs Shape

There is a wide range of bulb sizes, each with a particular use and appearance. Although bulb shape generally comes down to personal preference, some fixtures can only fit specific bulb shapes so it is important to pay attention.

What is the most common light bulb shape? ›

1. A Series Bulbs. A group stands for arbitrary and the arbitrary bulbs are also called the A-type lamp which is denoted with an A. The A-shape light bulb is the most common light bulb for general home lighting applications such as desk lamps, ceiling fans, and closets.

How do you tell if a light bulb is LED or incandescent? ›

Additionally, observe the bulb's appearance while off. LEDs typically have a cluster of small diodes, whereas incandescents have a visible filament. When lit, LEDs emit an instant, bright light, while incandescents often have a warm-up time and a softer glow.

What does type S light bulb mean? ›

Type S doesn't refer to the mount; rather, it indicates the shape. Type S light bulbs are shorter, rounder-shaped bulbs that can use the same mount as a Type A or Type B light bulb.

What is the difference between E26 and E27? ›

The E26 is the standard thread size group for bulbs in North America. In Europe it is E27. The number following the letter E is the diameter of the external thread screw in mm. So, for an E26 bulb, the diameter of the base is 26 mm, while the E27 has a base diameter of 27 mm.

Are there different light bulb sockets? ›

There are two common socket types, which are the classic screw socket (Edison) and the pin socket.

Are E26 and E27 the same? ›

These two standards are interchangeable, meaning a US E26 will fit in a European E27 base, and E27 will fit in a E26 base. The only difference is the voltage (for light bulbs). In fact there is only 1 mm difference between the threads of E26 and E27, so they are virtually identical.

Do all light bulbs fit the same socket? ›

E26/E27 Medium – Edison 26-mm or 27-mm Diameter

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.

Are C7 and E12 bulbs the same? ›

Typically, C7 bulbs are made on an E12 sized base. C9 bulbs are made on an E17 sized base. They are so often manufactured in-line together that the terms for C7/E12 and C9/E17 are interchangeably misused. C7/C9 refers to the size and shape of the light bulb.

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