Common Light Bulb Base Sizes – Edison Screw

When replacing a light bulb, its helpful to know a bit more about it. In addition to knowing the voltage, wattage, color temperature and type of bulb, its also important to know that screw-in type bulbs come in several different diameters. The screw mounts are referred to as the Edison screw fitting, which of course was developed by Thomas Edison.


The designation for each type is Exx where the xx is the diameter in millimeters. These are the four most common types in the United States:

  • Candelabra: E12
  • Intermediate: E17
  • Standard: E26
  • Mogul: E39

The sizes are slightly different in other countries, but of course the big difference is that the voltage is also different so the bulbs are generally not interchangeable.


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