A19 Vs A21 Light Bulbs

A19 Vs A21 Light Bulbs

Shopping for light bulbs is not always an easy task, as there are a variety of different sizes and styles to choose from. Even if you just want a regular 100-Watt LED light bulb, you will probably come across a myriad of options. Two of the most common options are the A19 and A21 variations. The A19 is often considered to be the “standard” bulb for most households, but it is not the only style that you can use in your home light fixtures, since A21 is a highly versatile and popular option as well.

So, this begs a few important questions. What are the differences between A19 and A21 light bulbs? Are A19 and A21 bulbs interchangeable? Most importantly, when it comes to the A21 vs A19 bulb, which is actually the best option for you?

In today’s guide, we will answer all of these questions and more, but first, let’s examine all of the different types of A-type bulbs on the market.

What Is The A-Type Light Bulb?

The A-type light bulb is the standard, pear-shaped light bulb that can be screwed into standard, E26 light fixtures. These light bulbs have been around for more than a century and have become commonplace in most homes and many businesses. The “A” signifier only refers to the shape, so A-type bulbs can be incandescent, CFL, or LED. However, A-type LED bulbs are becoming increasingly popular due to their long lifespan and energy efficiency.

The number that follows the “A” signifies the bulb’s diameter in eighths of an inch. For example, the most common A-type bulbs are A15, A19, A21, A23, and A25. This means that you can simply take the number and divide it by 8 to find out the diameter of the bulb. You can see the exact measurements in the chart below:

Bulb Type




1.875 inches

3.39 inches


2.375 inches

4.13 inches


2.625 inches

5 inches


2.875 inches

5-6 inches


3.125 inches

6-7 inches

While you can usually find all of these bulbs for sale online or at a hardware store, the most common A-type bulbs are A19 and A21. This is largely due to the fact that both bulbs offer the best combination of brightness and versatility. They are not too small to fully light most rooms, nor are they too big to fit comfortably into most light fixtures.

What Is The Difference Between A19 and A21 Bulbs?

If you were to make a direct visual comparison, it is readily apparent that A21 and A19 are different sizes. As listed in the table above, the widest segment of an A19 bulb is 2.375 inches, while the widest segment of an A21 bulb is 2.635 inches. Though this may not seem like a huge difference, it becomes a much starker contrast when you factor in the height differences. A19 bulbs are 4.13 inches tall, while A21 bulbs are roughly 5 inches tall. Thus, the biggest and most obvious difference between A21 and A19 bulbs is the size.

However, people often assume that since the bulbs are different sizes, they must not fit into the same light fixtures. Fortunately, this is not the case. Regarding compatibility with light sockets, A21 and A19 are interchangeable. This means that you can still use either type of bulb in most standard lamps that require an E26 Edison screw. That said, you may be able to screw in the bulb, but if your light fixture has a small enclosure or lamp head that does not accommodate a larger bulb, you may have no choice but to go with the A19.

Are A21 Bulbs Brighter Than A19? Why Is The A21 Bulb Better Than The A19?

While A21 and A19 are interchangeable bulbs, this does not mean that they produce the exact same results. In fact, their size differences are not purely aesthetic. If you want a 100-Watt bulb (or higher) to produce more light, then you may also need to get a larger size bulb. This is due to the fact that more light creates more heat. In a smaller bulb, there is less surface area through which the heat can escape, which could cause damage to the internal electronics (particularly with LED lights). For this reason, A21 bulbs typically have higher wattages and therefore produce more light. At the same time, the increased size helps mitigate the heating issue entirely.

Overall brightness and size are not the only factors you should consider when choosing between the A21 and A19 bulbs. You should also think about the layout and size of the room in which you plan to use the bulb, how the light will be distributed, as well as your budget for utilities. For example, most homes or apartments require ample lighting in the kitchen area, with dimmer or warmer lighting in seated areas and bedrooms. While both A19 and A21 bulbs produce 360-degree beams with omnidirectional illumination, they do not fill the same amount of space with light.

A21 bulbs can accommodate higher wattages (and therefore produce more lumens), emitting stronger, brighter light than A19 bulbs. As you can imagine, this also means that A21 bulbs use more energy. While LED bulbs of any kind are often the most cost-effective and energy-efficient bulb option, choosing A19 over A21 will almost certainly save you money on your monthly electricity bill. Nonetheless, if you have rooms or areas of your house that require strong, bright lighting, A21 bulbs are the superior option.

Why The A19 Bulb May Be Better Than The A21 For You

As previously mentioned, the A19 and A21 bulbs are interchangeable insofar as they both fit into the standard E26 socket that most light fixtures use. However, the design of your light fixture could ultimately determine which bulb is best for you. This is due to the fact that A19 has been the standard bulb size for more than 100 years. As a result, most lamp and light fixture manufacturers have designed their products to accommodate the height and width of the A19.

So, if you’re just looking to purchase a new set of bulbs that will work in a wide range of fixtures and rooms in your house, the A19 is a great option. It is the standard and therefore will fit in any standard fixture without the need for any modifications. Alternatively, you could run into issues trying to fit an A21 bulb into smaller lampshades, frames, or harps. Depending on the material of your lampshade, you could even create a hazardous situation if a larger bulb comes into contact with the shade itself for a prolonged period of time.

In addition to its compatibility with most standard sockets, frames, harps, and shades, the A19 is also more economical. It is not as bright (but still produces adequate light), does not produce as much heat, and uses less electricity than the A21. This means that if you want a well-lit room without having to pay higher electricity costs, the A19 is the better bulb for you.

Are you interested in learning more about A19 and A21 bulbs? Are you ready to purchase high-quality LED bulbs at affordable prices? If so, be sure to check out the products available at Bulb Center today!

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