A19 vs A21 Bulb

A19 vs A21 Bulb – A Quick Comparison Guide

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Should you get an A19 or an A21 bulb? Check out the differences between an a19 vs a21 bulb first with our comparison guide, so you’ll know which suits you.

A19 vs A21 Bulb
A19 vs A21 Bulb | KRM Light+

If you’ve gone over to the light bulb section at the hardware store, you’ve probably seen bulbs with sizes like A19 or A21. What exactly is the difference between these two sizes and how does the size difference affect how you choose anyway? 

You may not know it, but size plays a huge role in bulb and socket compatibility. That’s why you need to familiarize yourself with these two common bulb sizes. We’ll be talking about the difference between a19 vs a21 bulb, as well as some of the applications used by A19 vs A21 bulbs.


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A21 LED Bulb Reviews


A19 Vs A21 Bulb Comparison

To start it off, it is first important to know what is a19 vs a21 bulb. As already mentioned earlier, A19 and A21 refer to the size of the bulb. Just to give you an idea, the A refers to a standard size type of lightbulb that is used for most homes. This is the pear-shaped type of lightbulb that uses an E (Edison) sized base. In other words, they come from the same shape type but differ in size. 

Comparing the two types of bulbs means that you need to compare the a19 vs a21 bulb shape. From a distance, there may not seem to be any differences between the A19 vs A21 bulb. However, further examination of the bulbs will show you that there is a slight difference in the size of the bulb head.

The A19 A21 Bulb Dimensions Are As Follows:

The A19 has a diameter of 2.375 inches and a height of 4.13 inches. On the other hand, the A21 bulb has larger dimensions of 2.6225 inches in diameter and 5 inches in height. 

While size may be the main and most obvious difference between the two bulbs, they also have a difference in power. Now, a bulb’s power is usually measured in lumens. Lumen refers to the illuminating power a bulb emits when you turn it on. Obviously, an A21 bulb will be able to produce a higher number of lumens as compared to an A19 sized one because the A21 bulb has a bigger space for heat dissipation. This is especially true for LED lights of these sizes since LED lights are extremely powerful.

Now that you know the differences between the two, you might be asking if there are any significant similarities that we need to take note of. Aside from the shape, they both use the same type of base for the socket. That’s why you can pretty much use either one for residential purposes like table lamps, ceiling fan lights, basement lights, and the like. 

A19 Vs A21 Bulb Applications

Since they have the same base, you may be thinking that it won’t really make a difference choosing between the 2 since they can be used interchangeably anyway. While this is actually true to a certain extent, knowing the differences between an A19 vs A21 bulb will help you work around heat dissipation issues, as well as energy efficiency issues. 

As we have already established, the A21 bulb can have a higher lumen level since it has a bigger space for better heat dissipation. Because of this bigger size, manufacturers actually tend to make stronger lights of up to 100W using this size of the bulb. So, if you’re looking for a strong bulb for let’s say, your basement, your lamp, or a big living room lamp, then you might want to use A21 bulbs for these purposes. 

However, you may want to take note that this sort of power also comes with a price– energy efficiency. For the most part, A21 bulbs that have added lumen power in it will really result in a higher energy bill. Since most A21 bulbs these days are packed with power, you may want to reconsider using them if you don’t need such strong lighting and if you want to save money. That said, the more energy-efficient option would be the A19 bulb.

Want to know the difference between shunted and non-shunted socket? Read HERE!


As a buyer, you may not really see the significance of differentiating the two, but it will help if you know the pros and cons of the A19 vs A21 bulb. Even though the main difference between the two is really the size, the overall size of the bulb may actually affect the power, as well as the energy consumption of the bulb.

Hence, for those who are very particular with the numbers, you really have to take note of these small details. Taking note of these small things will really be able to help you understand more about your lighting system in the long run. 

If ever you’re curious about the two types or if you just want a deeper understanding of them, then always keep our comparison guide in mind.

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