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A19 vs A21 Bulbs 

Bulbs that feature the letter code “A” in their name are designed for residential light fixtures. The numbers used indicate their sizes. The A19 and A21 household bulbs are built for a multitude of purposes and fixtures. They both feature a standard base that secures the bulb in light fixtures such as a ceiling fan or table lamp.

The A21 bulb is larger than the A19 bulb. Both look alike and come with a nominal power of between 40 and 60 Watts. This helps to produce between 450 and 800 lumens.  Homeowners that would like to have brighter lights can opt for incandescent bulbs that have a nominal power of about 100 Watts.

Manufacturers across the globe are working to produce LED bulbs that produce as much light as 100-Watt incandescent bulbs. Their aim is to make them energy efficient and eliminate prevalent heat issues that arise when an LED light bulb produces too much light.

A19 Description


The A19 bulb has a diameter of 2.375 inches and a height of 4.13 inches. It’s smaller than the A21 bulb. The diameter is arrived at by dividing the number indicated on the bulb by eight. That is, 19/8 = 2.37.

In millimeters, the bulb has a diameter of 69.5 mm and a length of 112.7 mm. Countries that use the metric system also refer to the A19 bulb as A60. This is to represent its diameter. A19 bulbs have dimensions governed by the ANSI C79.1 guidelines in North America.

All A19s use an E26 base. It’s important to note that not all bulbs that have the E26 base are A19s. Your bulb may offer a different brightness depending on the amount of power it consumers.

a19Strong Sides

1. Light instantly.

2. Available in multiple color temperatures.

3. Can last up to 15,000 hours of use.

4. Environmentally friendly.

5. Doesn’t produce ultraviolet or infrared radiation.

Weak Sides

1. Might be difficult to set up where smart technology is included.

2. May have poor color quality.

A21 Description


The A21 bulb measures 2.6 inches in diameter and between 4.1 and 5.4 inches in length. In millimeters, it has a diameter of 78.5 mm and a length of 139.7 mm. It is slightly larger than the A19 bulb.

The A21 bulb has adequate capacity to house higher-lumen LEDs due to its ability to get around the heat issues that affect smaller bulbs. It has enough surface area for the heat to escape. This helps to protect the sensitive internal components.

A21 bulbs are also less complicated to make and comprise the largest number of energy-efficient light bulbs for residential use.

a21Strong Sides

1. Bright enough for outdoor use.

2. Lights up quickly.

3. Dimmable.

Weak Sides

1. May not be durable.

2. May flicker and not light consistently.


If you want a larger bulb, go for the A21. If you want a smaller bulb, go for the A19. Despite the two having the same base, it’s not advisable to interchange them. It’s important to note that the A19 can fit into an A21 lamp socket, but the vice versa isn’t true.

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