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E26 vs. A19: What’s the Difference?

Power saving concept. Asia man changing compact-fluorescent (CFL) bulbs with new LED light bulb.

E26 vs. A19: What’s the Difference?

Key Points

  • E26 and A19 are both standard specifications for light bulbs, with E26 referring to the base diameter and A19 indicating the bulb shape and diameter.
  • E26 bases have a diameter of 26 millimeters and can hold a variety of bulbs, while A19 bulbs have a pear-shaped design with a diameter of approximately 2.4 inches.
  • Both E26 and A19 bulbs are commonly used in residential and commercial settings, with E26 being more common in commercial applications.
  • The length of an A19 bulb can vary between 3.9 and 4.3 inches, depending on the specific product.
  • The dimensions of E26 and A19 bulbs are set by the American National Standards Institute (ANSI).

When tech and DIY combine, it can leave us with a lot of headaches. Even once you’ve researched and understood one aspect of what you’re looking for, unexpected specs can throw you for a loop. Adding to the confusion is the naming conventions that manufacturers use. While these are intended to simplify matters, and they can certainly give you a lot of information, knowing what they mean isn’t always intuitive. If you’re reading this, you’re probably looking to purchase some new light bulbs. You may have assumed that “E26” and “A19” mean the same thing, or maybe you’re simply confused about these terms altogether. Don’t worry, we’re going to break down what both of these terms mean, compare the differences, and shed some much-needed light on your situation!

E26 vs. A19: Side-By-Side Comparison

CategoryE26A19
Naming conventionNamed after Thomas Edison (“E”,) number refers to base diameter“A” means “arbitrary” and refers to bulb shape, number refers to bulb diameter
Measurement26 is the diameter of the base in millimetersMeasured in 1/8 inch increments. Diameter is 19/8 = 2.4”
Bulb shapeCan be a variety of shapes depending on which bulb is usedPear-shaped, wider at the top
Dimensions26 mm across baseTypically 3.9 – 4.3 inches in length, 2.4-inch diameter at widest point
Alternative NamesAlso called a “Medium Edison Screw”, as it’s medium-sized in the range of E-type bulbsCan also be called an “A60” bulb, referring to the diameter in millimeters
Date of Introduction1909Early 20th century

E26 vs. A19: What’s the Difference?

Some of the main specs of E26 and A19 are in the table above, but a further explanation will be useful at this stage. Below, we get into the specifics, and what sets E26 and A19 apart.

Naming

First things first, let’s get into what the terms themselves mean. You’d be forgiven for thinking “E26” refers to a specific type of bulb. After all, if you search for E26 in any retailer, you’ll find bulbs being marketed as E26. However, this is a little misleading. In reality, E26 refers to the structure of the base of the bulb, not the bulb itself. In this way, “E” stands for Edison, as Thomas Edison developed these screw bases. The number after the “E” indicates the base diameter. So, in the case of E26, we have an Edison screw base with a diameter of 26 millimeters. Simple enough!

Let’s compare it with “A19.” Now, the letter and numbers here also indicate the type, but the naming convention is different to E26. The “A” either stands for “arbitrary” or “A-series”, and indicates the shape of the bulb. An “A” bulb is a classic pear-shaped bulb (an upside-down pear, that is.) The number gives us the diameter in this case too, but the way this is measured differs from E26. Instead of referring to the diameter in millimeters, this measurement is usually given in eighths of an inch in the U.S. Therefore, “19” means 19 eighths of an inch, or 19/8 inches. This is equivalent to 2.4 inches. In other parts of the world, this number may be given in millimeters, but this is uncommon in America.

All in all, most A19 bulbs in the U.S. will have an E26 base, which is why they’re often synonymous. However, this isn’t always the case, and lots of bulbs can have an E26 base. So, if you ask for an “A19” or “E26” bulb, you may not get what you expect.

kilowatt hour vs watt
While “E26” refers to an Edison base, “A19” refers to a standard pear-shaped bulb.

Dimensions

As mentioned, E26 doesn’t refer to the size or shape of the bulb. Therefore, it’s possible to have many different bulbs designated with E26 that have completely different measurements. Although Edison bases come in a lot of sizes (ranging from E5 to E40), all E26 bases have the same diameter of 26 millimeters. The standard for most bulbs is either E26 or E27, and both of these are interchangeable. You’ll commonly find E26 bases to have A19 bulbs as well since this is also a standard specification, but this isn’t a certainty.

Since A19 refers to the bulb specifically, this tells us information about the bulb’s shape. As we said in the previous section, an A19 bulb is pear-shaped, with its widest point measuring 2.4 inches in diameter. As such, every A19 bulb you come across will have this shape and this width. However, this doesn’t mean that every A19 bulb has the same measurements. The bulb length can vary considerably, from around 3.9 inches up to 4.3 inches, depending on the specific product. Often, the wattage of the bulb will determine the length, following standards set by the American National Standards Institute (ANSI.) But, in general, the diameter of an A19 bulb is pretty consistent, maybe varying by one to two millimeters.

Uses

Since the E26 is a standard base type, it naturally has a lot of applications. While you’ll typically use A19 bulbs with an E26 socket, you can also use other types, including A21 bulbs, as well as BR and PAR lamps. All kinds of bulbs, from incandescent and LED to CFL and halogen can be compatible with E26 sockets. In addition, smart bulbs are often compatible with E26. These sockets are also common in commercial applications and workspaces. Bulbs screw into E26 bases easily, which provides a versatile and secure foundation for you to install your bulbs with no special equipment required. If you’ve got a lamp or bulb to fit, there’s a good chance it’s compatible with E26.

Similar to E26, since A19 is a standard bulb specification, its usage is fairly versatile. As such, you’ll find A19 bulbs that are compatible with lamps, ceiling fixtures, smart lighting systems, sconces, and more. A slight difference is that A19 bulbs tend to be less common for outdoor fixtures, although you can find special A19 bulbs that are specifically for outdoor use. A19 bulbs are also found in household applications most of the time, rather than professionally. You can find A19 bulbs of various kinds, such as incandescent, energy-saving LED, halogen, or CFL, which are generally interchangeable. Having an idea of what kind of lighting you’re looking for before going shopping is a good idea.

Modern dimmer light switch used being lowered for dimmer lighting and to save electricity
Both E26 and A19 are commonly found in household lighting systems.

E26 vs. A19: 7 Must-Know Facts

  1. E26 refers to a Medium Edison (“E”) Screw, which is a type of bulb socket. “26” refers to the diameter of the screw base in millimeters
  2. A19 refers to a standard bulb shape and size, with “A” standing for arbitrary. “19” means the diameter of the widest point of the bulb in eighths of an inch (i.e., approximately 2.4 inches)
  3. Both E26 and A19 are standard specifications and some of the most common
  4. In practice, the vast majority of A19 bulbs fit into E26 bases, but E26 bases can hold a large variety of bulbs aside from A19
  5. Both have similar uses, although E26 is more common than A19 in commercial settings
  6. The length of an A19 bulb can vary considerably, from around 3.9 inches up to 4.3 inches
  7. Standards for the dimensions of E26 and A19 are set by the American National Standards Institute (ANSI)

Frequently Asked Questions

What's the difference between E26 and A19?

E26 refers to a type of screw base that light bulbs fit into, whereas A19 refers to a specific bulb shape. Therefore, although the terms are often used together, they don’t refer to the same thing.

What Do E26 and A19 mean?

“E26” bases were developed by Thomas Edison, hence the “E” in the name. As a medium Edison screw, the 26 refers to the diameter of the base in millimeters. “A19”, on the other hand, refers to a specific size and shape of the bulb. The “A” stands for “arbitrary” or “A-series”, which is a standard pear-shaped bulb. The number refers to the diameter of the widest part of the bulb in eighths of an inch, i.e., 19/8 inches, or approximately 2.4 inches (or 60 millimeters.) This is why A19 is usually referred to as A60 in Europe.

Are E26 and A19 interchangeable?

A lot of the time they are, and A19 bulbs are often listed with E26 in the name. However, technically, they’re not interchangeable terms, since E26 refers to the socket base and A19 refers to the bulb itself. Most of the time, A19 bulbs will be compatible with an E26 base, but this isn’t guaranteed. Likewise, E26 bases are compatible with a lot of different kinds of bulbs, so you may not find what you’re looking for by asking for an E26 base.

Can I replace one A19 bulb with another?

Yes, generally, you can replace one A19 bulb with another kind of A19 bulb. For example, you can replace an incandescent A19 bulb with an LED A19 bulb, or an LED with a CFL. However, the wattage rating may differ (meaning the brightness will be higher or lower) as well as the appearance of the light, so be sure to check these before making the switch.

What's the most energy-efficient type of bulb?

CFL and LED bulbs are both more energy-efficient than a standard incandescent bulb. However, LEDs are generally around three times more efficient than CFLs and tend to be the most long-lasting and durable of all the bulb types.

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