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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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10 comments

  • Absolutely crystal clear explanation, unlike many others on the web. Thank You.

    Bill Ng on
  • Pretty scary to see the ratio on Ebay of E27 listings to E26 be something like 2:1. Ebay should ban sales of E27 bulbs in the USA due to fire and electrical hazards. China makes E26 bulbs too so I wonder why so many sellers are selling that junk so cheaply. People really need to do their research before bringing dangerous electrical items into their homes.

    Matt on
  • Sounds like Mike Gaba did not actually read/understand the article by saying that. Because if you had read the article, you’d know that A19 and E26 are not even the same thing. Since they are not the same thing, you cannot determine if they are interchangeable. It’s like asking if pants with a 36 inch Waist are interchangeable with pants with 32 inch inseam. APPLES and ORANGES.

    King Skullie on
  • Good and concise article! Commenter Mike Gaba clearly did not ready the article, is a troll, or has no reading comprehension skill.

    Neditor on
  • Mike, A19 and E26 are not interchangeable — one is the shape of the bulb, one is the base type. In the USA, an A19 typically has an E26 base, used in what most of us think of as a light bulb socket. But there are other types of connections too, requiring different bases.

    Steve on

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