Light Bulb & Socket Guide

Light Bulb & Socket Guide 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. 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 Dimensions

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 for our decorative string lights:

*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.  

Bulb Comparison - G30, G40, G50 Globe Sizes

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

Bulb Comparison - G40 & G50 in C7 and C9 Socket Sizes

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

Bulb Comparison - G50 in three socket sizes

Bulb Shopping

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