Differences: Light bulb A17 vs A19 vs A21

Light bulbs are devices that emit visible light using electric energy. They have become an essential part of our modern society and a common form of artificial lighting. Light bulbs are easily replaceable and can be removed from light fixtures when they fail or when you need better bulbs. What is the difference between A17 vs A19 vs A21, and what to know each about?

light bulb types and differences
Light bulb

Depending on purposes and consumer preferences, bulbs are made in different sizes and shapes. Here are types of light bulbs, based on their shapes:

  • A (Arbitrary) Type: A-type bulbs are called arbitrary because they look like regular bulbs with a ball-like shape. These bulbs are usually used for household uses and in basic fixtures where the whole bulbs are visible. A number of A-type bulbs refer to their diameter in one-eighth of an inch. An A17 bulb has 17/8-inch or 2.125-inch in diameter, while an A21 bulb has 21/8-inch or 2.625-inch in diameter. A-type bulbs are traditionally incandescent, but it’s now common to find those with CFL and LED technology. Due to their shape, A-type bulbs emit Omni-directional light making them useful for general or ambient lighting.
  • B (Blunt Tip) Type: B-type bulbs have a narrow, bullet-like shape. Contrary to the A-type bulbs, they bulge at the base and taper to a pointy tip. This makes B-type bulbs suitable for general or ambient lighting because much of the light is emitted 360-degree on a horizontal orientation. B-type bulbs can be incandescent, halogen, CFL, or LED. Due to their pointy shape, B-type bulbs are often used for decorative purposes as pendant lights, wall sconces, or chandeliers. Low-wattage B-type bulbs are more suitable for decorative or accent lighting.
  • C (Candle) Type: C-type bulbs are cone-shaped with bent tips, so they look like the flicking flame of a candle. They are also available as incandescent, halogen, CFL, or LED bulbs. The flame-like shape of C-type bulbs makes them more suitable for decorative elements in pendants, light strands, and chandeliers. Low-wattage C-type bulbs are usually used as night lights.

A17 light bulb

A17 is an A-type light bulb with a regular ball shape. Based on its naming, the diameter of the A17 bulb is 17/8-inch or 2.125 inches. The length of A17 bulbs varies depending on the models and manufacturers. However, a proportionally-shaped A17 bulb is usually about 4-inch long, while the base element is about 1-inch long. Technical specifications also vary depending on the type of bulb. However, an A17 LED bulb usually has power and current consumption of 3 Watts and 0.03 Ampere, respectively. With such power consumption, the bulb should have a lumens value of 200. Because A-type bulbs are omnidirectional, the color of the light is usually halogen white with a temperature of around 2,500K.

The typical operating temperature of an A17 LED bulb is between -25 and +40 degrees Celsius. It usually has a heatsink element to absorb excess heat, which is typically made of aluminum.

The bulb is made of glass with frosted white color. Many A17 LED bulbs are dimmable with an adjustable current to control the power consumption and light emission. Depending on the manufacturer, A17 bulbs may last for 25,000 hours of continuous use, but some can last for 50,000 hours. If you choose an A17 bulb from a reputable manufacturer, the warranty usually lasts for two years.

A19 light bulb

A19 is an A-type light bulb with a regular ball shape. Based on its naming, an A19 bulb has a diameter of 19/8-inch or 2.375-inch. There are many A19 bulbs in stores, but a proportionally shaped is usually around 4.1-inch long. Technical specifications of A19 LED bulbs depend on their models and they usually have slightly higher power consumption than A17 bulbs. An A19 light bulb with 7 Watts of power consumption and 0.065 Ampere of current consumption usually produces around 700 lumens. Due to their omnidirectional orientation, A19 bulbs usually have halogen white light with a color temperature of around 2,700K.

Just like other A-type bulbs, a typical operating temperature of an A19 LED bulb is between -25 and +40 degrees Celsius but can be slightly higher. The bulb is usually made of glass and frosted white. It usually has a heatsink above the contact element to absorb excess heat during long-term operations. A19 LED bulbs are usually dimmable, with an adjustable current to control the luminosity. Reputable manufacturers often offer a two-year warranty for A19 bulbs, which is a good deal, considering that these bulbs often last for more than 3 years, if they are turned on continuously for 24/7. Be sure that the A19 bulb has a rated lifespan of 25,000 hours.

A21 light bulb

A21 is an A-type light bulb with a regular ball shape. Based on its naming, an A21 bulb has a diameter of 21/8-inch or 2.625-inch. Other details of the dimension vary depending on the manufacturer, but a proportionally-shaped A21 bulb is usually around 5.2-inch long. Due to its size, the A21 LED bulb usually has a slightly higher power consumption at around 9 Watts and current consumption of 0.09 Ampere. With the increased power consumption, A21 LED bulbs may produce more than 800 lumens. A21 bulbs emit light omnidirectionally, which makes them suitable for general or ambient lighting. You may find variants with Halogen White (2,700K) or Warm White (3,200K) light, which is ideal to illuminate a larger area.

The operating temperature of A21 bulbs is between -25 and +40 degrees Celsius. If you want to use an A21 light bulb for exterior use, be sure that it meets the IP63 rating for proper waterproofing. The bulb is usually made of glass, but you may choose one made of polycarbonate for better durability. The heatsink material is usually made of aluminum, which has good thermal conductivity. Depending on the manufacturer, the expected lifespan is between 25,000 and 50,000 hours. An A21 bulb usually weighs 0.5lbs with a 3-year warranty.

Differences A17 vs A19 vs A21

The main difference between A17 vs A19 vs A21 bulbs is actually in diameter. Remember, each bulb has a different size in diameter. Therefore, this table presents each bulb size:

Bulb TypeSize in diameter (Inches)Size in height (Inches)
A1717/8 = 2 1/8 = 2.125 inches
A1919/8 = 2 3/8 = 2.375 inches4.13 inches
A2121/8 = 2 5/8 = 2.625 inches5 inches
A2323/8 = 2 7/8 = 2.875 inches3.2 inches
A-type bulb sizes
Different bulb shapes A17 vs A19 vs A21 vs A23
Different bulb shapes A17, A19, A21, A23

Why do they make different size bulbs in the first place? A 100-Watt or 125-Watt light bulb needs a higher surface to dissipate heat. Therefore, manufacturers usually make high-Watt bulbs in a bigger form. Contrary, 40-Watt, or 60-Watt bulbs can be found in a smaller form-body.

One key characteristic between these bulbs is that the bigger the bulb is, the higher the wattage rating is able to hold, due to its capability to more effectively dissipate heat.

Light bulb sizes and differences: A17 vs A19 vs A21. As we told before, this designation mark represents a bulb size in diameter. Therefore, the A17 light bulb has 2 β…› inches in diameter, A19 2 β…œ, and A21 2 ⅝ inches.

Final words

Due to their shapes, A-type bulbs are usually not intended for decorative purposes. Instead, they have functional purposes to illuminate your indoor or outdoor space. If you want a brighter light, choose bulbs with higher lumens value. The larger the bulb, the higher its power consumption and luminosity. For indoor lighting, you need at least 500 lumens for a medium-sized room and 700 lumens or more for a large room or living room. Consider using at least an 850-lumen A-type bulb for outdoor lighting. Whether you choose an A17, A19, or A21 bulb, depends on personal preferences and requirements.

Before ending this topic, we want to encourage you to replace all the bulbs with a LED-appropriate model. That way you’ll improve your home significantly and save your electrical bills also.