Light Bulb Bases

Use this handy guide to identify different types of light bulb bases that apply to incandescent, halogen, high-intensity discharge, fluorescent, and LED light bulbs. Click on any of the illustrations to view a list of bulbs with that light bulb base. If you do not see the base type you are looking for, give us a call at 800.784.1998, and we can help you locate the correct bulb.

Lighting Tip: in some older light bulb catalogs, bases are referred to as "caps."

About Light Bulb Base Types

There are dozens of base types for light bulbs, most of them made up of a series of letters and numbers. Decoding these is often no easy task for consumers and professionals.

Click on any of the base illustrations above to see a list of light bulbs that have that base.

Edison Screw Bases

The most common bases everyone is familiar with start with an E, signifying "Edison" type screw bases. The number after the E represents the diameter of the base in millimeters.

Here are some examples of Edison bases and their more commonly-known names.

  • E39 - Mogul
  • E26 - Medium
  • E17 - Intermediate
  • E12 - Candelabra
  • E11 - Mini Candelabra
  • E10 - Miniature
  • E5 - Midget

Most Edison base bulbs have a single contact at the center of the base. Some special bases are double contact, and their base adds a "d" at the end (E26d, for instance).

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