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What is the difference between E26, E27 and A19?

Posted by Sales Team on

Shoppers of LED Light bulbs often confuse the specifications for base type (E26 or E27) and bulb shape (A19). 

Base Type

E26 E27 LED Bulb Base

Screw in bulbs use a base called an Edison Screw or ES base. This base was developed by Thomas Edison for the first light bulbs and is still in use today.

There are four commonly used thread size groups for lamps:

  1. Candelabra: E12 North America, E11 in Europe
  2. Intermediate: E17 North America, E14 (Small ES, SES) in Europe
  3. Medium or standard: E26 (MES) in North America, E27 (ES) in Europe
  4. Mogul: E39 North America, E40 (Goliath ES) in Europe.

The number following the E indicates the size in mm of the external thread screw. Thus a E26 has a 26 mm base diameter. 

You may see low cost LED bulbs using an E27 base on eBay and Amazon from foreign suppliers. While these technically will work in E26 bases, this is usually a sure indication that the bulb was not strictly designed for the US market and this bulb may lack a proper North American, UL or ETL safety certification and therefore should be avoided. 

Bulb Shape

Now that we have learned that E26 and E27 are terms used to describe the type of base used what does A19 or bulbs with an A designation mean?

A type describes a bulb that has a pear-like shape. The number that follows the "A" within the A series indicates the width of the bulb in one-eighth inch units or in millimeters.

The most commonly used A-series light bulb type is the A19 bulb which is 2 38 inches (60 mm) wide at its widest point and approximately 4 38 inches (110 mm) in length. This is the classic shape that most people are used to when shopping for a "Light Bulb". You can use this handy image below to identify the size of your A Shaped bulb:

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  • THANK YOU! Clear. Concise. Layman’s language. Awesome. Your article didn’t assume the reader is ignorant – just uninformed and seeking guidance to be able to make appropriate purchases for their lighting needs.

    Suzanne on
  • Awesome. You saved me time and money.

    Janice E Hoffman on
  • Thank you for this information. I was going nuts trying to figure out if I had the correct bulbs when they call out A19 medium base on the installation instructions. Good job!

    Donnaraec on
  • Thank you for your very helpful information.

    Peter on
  • This was so informative. Everything I needed to know! Buying a lamp online and wanted to make sure the bulb was standard. I had to look up the sizes to double check. This article told me everything I needed to know! Thank you!

    JB on

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