A19 vs A21: Understanding the Differences in Light Bulb Sizes

Choosing between A19 and A21 light bulbs may seem confusing because of their many similarities. These types, despite looking similar, differ primarily in size as an A21 bulb is generally larger than an A19.

This blog post will delve into the specifics to help you understand these differences, guiding your choice for home or office lighting. Get ready; it’s time to shed light on this topic!

Key Takeaways

  • A19 bulbs are smaller in diameter and height compared to A21 bulbs.
  • A19 bulbs typically have a medium screw base (E26), while A21 bulbs may have a larger medium screw base (E27) or mogul screw base (E39).
  • A19 bulbs are commonly used as standard household bulbs, while A21 bulbs are often used in larger spaces or areas that require brighter lighting.
  • A21 bulbs are generally brighter than A19 bulbs and offer better energy efficiency.

Understanding the Difference in Light Bulb Sizes

The terms “A19” and “A21” refer to different sizes of light bulbs, with A19 being smaller in diameter and height compared to A21 bulbs.

What do “A19” and “A21” mean?

“A19” and “A21” are labels for light bulb sizes. The “A” stands for the shape of the bulb, which is a common pear-like shape. The numbers that follow tell us the size. An A19 bulb is smaller, with a width of 2.375 inches and it stands 4.13 inches tall.

But an A21 bulb is bigger than an A19. It measures 2.625 inches across and is 5 inches tall.

Size comparison: A19 vs A21 in diameter and height

When comparing the sizes of A19 and A21 light bulbs, two key parameters to consider are diameter and height. This difference in dimensions can affect their suitability for different fixtures and applications.

Light Bulb Diameter (inches) Height (inches)
A19 2.375 4.13
A21 2.625 5

As evident from the table above, the A19 bulb has a diameter of 2.375 inches and a height of 4.13 inches. It is often considered the standard household bulb. On the other hand, the A21 bulb is slightly larger with a diameter of 2.625 inches and a height of 5 inches. This larger size may require a bit more space in your lamp holder or fixture. So, the next time you plan to replace a bulb or light up a new lamp, keep these dimensions in mind to ensure compatibility and the desired illumination output.

Differences in bases used

A19 and A21 bulbs not only differ in size, but also in the bases they use. The base of a light bulb is the part that screws into the lamp holder or socket. A19 bulbs typically have a medium screw base (E26), which is the most common type used in household lamps and fixtures.

On the other hand, A21 bulbs often have a larger medium screw base (E27) or mogul screw base (E39). This means that A21 bulbs may require special lamp holders or fixtures that can accommodate their larger bases.

It’s important to consider the compatibility of the bulb base with your existing lamps when choosing between A19 and A21 bulbs for your lighting needs.

Compatibility in lamp holders

A19 and A21 bulbs may differ in compatibility with different lamp holders. This means that not all lamp holders or fixtures will be able to accommodate both bulb sizes. Here are some factors to consider when it comes to compatibility:

  1. Size of the lamp holder: A21 bulbs, being slightly larger in diameter and height, may require a larger lamp holder or fixture compared to A19 bulbs.
  2. Socket type: Ensure that the socket type of the lamp holder matches the base size of the bulb you intend to use. A19 and A21 bulbs can have different base types, such as screw-in (E26/E27) or bayonet (B22).
  3. Wattage limitations: Lamp holders have wattage limitations, so make sure the wattage of your chosen bulb is within the acceptable range specified by your lamp holder.
  4. Design and structure: The design and structure of certain lamp holders may only allow for specific bulb sizes or shapes. Check if there are any restrictions on bulb size mentioned in the product specifications or instructions.
  5. Adjustable features: Some lamp holders may have adjustable features that allow for different bulb sizes, while others may be fixed and only compatible with a specific size.

Different uses for A19 and A21 bulbs

A19 and A21 bulbs have different uses depending on their size and brightness:

  1. A19 bulbs are commonly used as standard household bulbs for general lighting in rooms such as living rooms, bedrooms, and kitchens.
  2. A21 bulbs, being larger in size and typically brighter, are often used in spaces that require more illumination like large living areas, dining rooms, or commercial settings.
  3. A19 bulbs are suitable for lamps or fixtures with limited space due to their smaller size.
  4. A21 bulbs may be a better choice for fixtures with larger dimensions that can accommodate their bigger size.
  5. Both A19 and A21 bulbs are available in various options such as incandescent, CFL, and LED types to suit different lighting needs.

Performance Factors: Brightness and Efficiency

A21 bulbs are generally brighter than A19 bulbs, making them a good choice for spaces that require higher levels of illumination. Additionally, A21 bulbs often offer greater energy efficiency compared to their A19 counterparts.

Are A21 bulbs brighter than A19 bulbs?

A21 bulbs are generally brighter than A19 bulbs. The brightness of a bulb is measured in lumens, and A21 bulbs typically have a higher lumen output compared to A19 bulbs. This means that A21 bulbs can provide more light and illuminate a larger area.

If you need brighter lighting in a room or space, choosing an A21 bulb would be a good option. However, it’s important to consider the size and compatibility of the bulb with your fixtures before making a final decision.

Advantages of the A21 bulb over the A19 bulb

The A21 bulb has some advantages over the A19 bulb. One advantage is that it produces more light because of its larger size. The A21 bulb has a higher lumen output, which means it can brighten up a larger space compared to the A19 bulb.

Another advantage is better energy efficiency. The A21 LED bulbs are designed to be more energy-efficient than their A19 counterparts, helping you save on electricity bills in the long run.

Additionally, the larger size of the A21 bulb allows for better heat dissipation, leading to a longer lifespan and less frequent need for replacement. So if you’re looking for brighter and more efficient lighting options, the A21 bulbs might be a better choice for your DIY projects or home improvement needs.

Considerations for choosing between A19 and A21 bulbs

When choosing between A19 and A21 bulbs, there are a few factors to consider. Here are some important considerations:

  1. Size: A19 bulbs are smaller in size compared to A21 bulbs. Consider the available space and compatibility with your lamp holders or fixtures.
  2. Lighting Needs: Determine the brightness and lighting requirements for your specific area. A21 bulbs may provide more light output compared to A19 bulbs.
  3. Energy Efficiency: LED options are available for both A19 and A21 bulbs, which offer energy efficiency and longer lifespan compared to incandescent or CFL bulbs.
  4. Purpose: Consider the intended use of the light bulb. A19 bulbs are commonly used as standard household bulbs, while A21 bulbs may be suitable for larger spaces or areas that require brighter lighting.
  5. Cost: Compare the prices of A19 and A21 bulbs, taking into account the initial cost as well as the potential energy savings over time.

Available Options: Types of A19 and A21 Bulbs

There are various options available when it comes to A19 and A21 bulbs, including incandescent, CFL, and LED options. Each type has its own features and benefits to consider.

Incandescent, CFL, and LED options

Incandescent, CFL, and LED bulbs are available options for both A19 and A21 bulbs. Here are some features and benefits of each type:

  • Incandescent bulbs: These traditional light bulbs produce a warm, yellowish light. They are inexpensive but less energy-efficient compared to CFLs and LEDs. Incandescent bulbs have a shorter lifespan and may need to be replaced more frequently.
  • CFL (Compact Fluorescent) bulbs: These bulbs use less energy compared to incandescent bulbs and have a longer lifespan. They are available in different light colors, including warm white and cool white. CFLs take a short time to reach full brightness.
  • LED (Light Emitting Diode) bulbs: LEDs are the most energy-efficient option. They provide bright light while using minimal electricity. LED bulbs have the longest lifespan among all bulb types. They are available in various color temperatures, from warm white to daylight.

Features and benefits of each type

A19 and A21 bulbs come in different types, including incandescent, CFL, and LED. Incandescent bulbs are the traditional ones that produce a warm glow but use more energy. CFL bulbs are more energy-efficient and last longer than incandescent bulbs. LED bulbs are the most efficient option, using less energy while providing bright light and lasting for a long time. LED bulbs also come in various colors, allowing you to choose the right hue for your space. Overall, each type has its own features and benefits depending on your preference for brightness, energy efficiency, or color options.

Interchangeability of A19 and A21 Bulbs

A19 bulbs can be used in place of A21 bulbs and vice versa, but there are factors to consider when making the swap.

Can A19 bulbs be used in place of A21 bulbs and vice versa?

A19 bulbs can sometimes be used in place of A21 bulbs, but there are a few things to consider. The main difference between the two is their size. A21 bulbs are slightly larger than A19 bulbs, so they may not fit properly in all lamp holders or fixtures.

However, if the lamp holder or fixture has enough space for a slightly larger bulb, an A19 bulb could work as a substitute for an A21 bulb. On the other hand, using an A21 bulb in place of an A19 bulb might result in it being too big and not fitting properly.

It’s important to check the specifications of your lamp holder or fixture before making any substitutions to ensure compatibility.

Factors to consider when swapping A19 and A21 bulbs

  • The size difference between A19 and A21 bulbs may affect their fit in lamp holders or fixtures.
  • Consider the available space in the fixture or lamp holder before swapping bulbs.
  • Check if the wattage and voltage requirements of the replacement bulb match those of the original bulb.
  • Ensure that the lumen output of the replacement bulb is suitable for your lighting needs.
  • Keep in mind that A21 bulbs may provide brighter illumination due to their larger size.
  • If using LED bulbs, consider the energy efficiency and lifespan of both A19 and A21 options.
  • Evaluate the desired lighting ambiance and aesthetics when choosing between A19 and A21 bulbs.


In conclusion, understanding the differences between A19 and A21 light bulb sizes is important when choosing the right bulb for your needs. The A19 bulb is smaller in diameter and height, while the A21 bulb is slightly larger.

Consider factors like compatibility with lamp holders and the space available before making your decision. Whether it’s for a household or commercial setting, knowing the distinctions will help you find the perfect lighting solution.


1. What is the main difference between A19 and A21 LED light bulbs?

The main difference between A19 and A21 LED light bulbs lies in their dimensions. The numbers 19 and 21 refer to their diameter in eighths of an inch.

2. Is there a height difference between these two bulb types?

Yes, there is a height difference besides diameter comparison in size variations when we speak about type A bulbs like A19 vs A21.

3. Can I use both kinds of bulbs interchangeably?

It depends on your lighting fixtures. Some may only fit one size due to the bulb measurements, still it’s crucial to know the right bulb dimensions before choosing.

4. Do the two different sizes have different wattage?

A19 vs A21 led bulbs could vary in wattages too along with variations in their hue compatibility owing to diverse LED technology used inside them.

5. Does bulb lifespan change depending on its size or type?

Bulb lifespan differs based more on how the LED technology has been utilized rather than solely relying upon whether it’s an A19 or an A21 Type-A bulb.

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