Light bulb A19 vs A21 review and compare

Let’s talk about light bulbs, and the differences between A19, and A21 bulbs. Bulb type A19 differs from A21 bulbs. Let’s see what’s the difference between them, and what does A19 and A21 designation stands for. Read the topic: light bulb A19 vs A21.

a19 vs a21 the difference between a19 and a21 bulbs
A19 vs A21

What does light bulb a19 vs a21 designation mean, how to recognize light bulb type, and which one to buy? Learn about bulbs and find out what is the difference between an A19 and A21 bulb.

A19 vs A21 Bulbs Size Difference

The main difference between these bulbs is actually size in diameter. They both have the same purpose and behave similarly. We use both types in our home, and they are designed for residential usage. This is why we are decided to give you some more details about each bulb type. Before we go any further, read about the A-series light bulb on the Wikipedia page.

Note: What you can read from Wikipedia is that the number that follows the “A” designation indicates the nominal major diameter of the bulb, either in one-eighth inch units in the United States or in millimeters in the rest of the world.

Like we wrote already, the main difference between A19 vs A21 bulbs is their size. Within the context of writing, we are talking about the diameter of the bulb:

  • A19 2 ⅜ inch
  • A21 2 ⅝ inch

As you can see, the A19 bulb is smaller than A21, but there is more to write on this topic.

Light Bulb (E26, E27…) Base Differences

It is quite easy to understand the bulb base differences. The number following the E indicates the size in mm of the external thread screw. Thus an E26 has a 26 mm base diameter, an E27 base has 27mm, and so on.

A light bulb with an E26 base is standard for the North American market. Try to find an appropriate light bulb when looking for a replacement product.

Light bulb standard – North America

  • Intermediate: Bulb base E17
  • Medium: Bulb base E26
  • Mogul: Bulb base E39

A19 Bulb Description

A-series bulb type describes a common bulb that we all known as a pear-like bulb shape. The number that follows a designation mark indicates the width of the bulb in one-eighth inch units or in millimeters. For example, the A19 bulb has 2 ⅜ inches in diameter.

This is the most used A-series light bulb when we are talking about residential bulb types. A19 light bulb has 2 3⁄8 inches in diameter (60 mm converted in metric system units).

Another value we all need to know is bulb base size. It has E26, E27, and so on, which represents the bulb base (Edison Screw) size. That screw on the bottom of the bulb is called an Edison Screw or ES base. It has been developed by Thomas Edison for the first light bulbs and is still in use today. It stands as a standard for bulb types.

A21 Bulb Description

Like we wrote before, the A21 bulb is slightly bigger than A19. It has a diameter of approximately 2.6 inches. In countries that use the metric system, A21 bulbs are also referred to as A67 bulbs. In that case, value 67 refers to the diameter in millimeters.

The length of an A21 bulb is typically 4.1-5.4 inches (105-140 mm), also slightly longer than A19 bulbs.

According to ANSI standards, A21 bulbs must always use an E26 base for mounting into a light fixture. A21 and E26 refer to different things, but in this case, you will find that all A21 bulbs use E26 lamp bases. This applies to A19 bulbs as well.

NOTE: Not all E26 bulbs will be of A21 shape. Some E26 bulbs come in shapes completely different from a standard A21 or any A-style bulb.

A19 vs A21 Bulb Comparison

Designations A19 and A21 indicate the size of the bulb. The letter “A” stands for the most commonly used size of the lightbulb in residential appliances. Both light bulb types are well known all over the world.

The A-shaped bulb is one of the oldest lightbulb designs. This design is popular for so many years, and still, it is the first choice for every home build.

Both types (A19 and the A21) have a similar appearance, although the A21 comes with a slightly bigger body form. The shape of bulbs and the medium base allow us to screw these into virtually all residential light sockets. The difference between A19 and A21 has been shown in the picture below.

If you’re looking for replacement bulbs in your home, it is good to know what type you’ll need. Let’s explain the difference between the A19 vs. A21 bulb shape.

Compare A19 vs A21 light bulb difference
A19 vs. A21 light bulb

At a first look, they may seem to have no difference, but a further examination of both bulbs will reveal that there is a slight difference, either the bulb head or bulb base. Different bulb sizes can be deciding factor when choosing an appropriate bulb.

A19 vs. A21 Product Dimensions

The A19 light bulb measures around 2.375 inches in diameter and 4.13 inches in height. The A21 bulb comes in at larger dimensions, 2.6225 inches wide and 5 inches in height. That’s the most obvious difference between them. Another thing that comes from that difference is the power rating difference. The light bulb produces light (Lumens) and a significant amount of heat. For better heat dissipation we need a greater surface, which means that the larger the bulb is, the more lumens we can get from it.

  • A21 bulb dimensions are 2.6225 inches wide and 5 inches in height
  • A19 bulb dimensions are 2.375 inches in diameter and 4.13 inches in height

Apparently, an A21 light bulb will produce more lumens as compared to the A19 bulb. This is because the A21 bulb has a larger space for heat dissipation.

A19 vs. A21 Similarities

Now, when you know the differences between these two products, let’s see what they have in common. What are the similarities between A19 and A21 light bulbs?

Apart from the shape, both bulbs come with the same type of base. That makes them compatible with the socket, and easy to replace. The base helps you to use either of these lightbulbs for residential purposes such as table lamps, basement lights, ceiling fan lights, garage door opener light modules, etc.


If you want a larger bulb, go for the A21. On the other way, if you want a smaller bulb, go for the A19.

Despite these two having the same base, it’s not advisable to interchange them. Keep in mind that the A19 can fit into an A21 lamp socket, but vice versa cannot. There is not only one difference between a19 and a21, which is why you need to know a bit more about those.

If you’re interested: read about coin batteries CR2016, CR2025, and CR2032.

What does A21 light bulb mean?

The number that follows the “A” designation indicates the nominal major diameter of the bulb, either in one-eighth inch units in the United States or it is shown in millimeters for the rest of the world.

What does A19 mean on a light bulb?

Just like we have written before, A19 light bulb has 2 3⁄8 inches in diameter for U.S. measurement standard, and 60 mm converted in metric system units.