C7 and C9 Bulbs: What Are the Differences?

1 comment by Scott Young

Differing Christmas lights in background

The holidays are nearly here, but there’s still plenty of time left to decorate your home if you haven’t yet. Winter festivities just aren’t the same without festive, twinkling lights draped inside and outside your home. 


However, with so many lighting products on the market, it’s easy to get tangled up when shopping for the best ones for your needs. For instance, some common questions we get around the holidays involve the difference between C7 and C9 bulbs


Both types are used for holiday lighting as well as landscape lighting and other applications, but they are not the same. We’ll delve into more about these lighting types below. 

What Is the Difference Between C7 and C9 Bulbs? 

The main difference between C7 and C9 bulbs is their size. C7 bulbs are smaller than C9 lights, and there are also a few slight differences between C7 and C9 bulbs in terms of bulb height and diameter as well as base width. 

What Are the Different Sizes of Light Bulbs for Holiday Decor? C7 vs. C9 Bulb Size

Bulb Type



Base Type

Standard C7 Bulb

Approximately 1 1/2 inches without the base

About 1 inch

E12 base (the same kind used in candelabra, night lights and makeup mirrors) 

Standard C9 Bulb

Approximately 2.25 inches without the base

About 1.125 inches

E17 base (also used as appliance bulbs and in desk lamps) 


A quick and simple way to tell whether the bulb you have is a C7 is to try to screw it into a night light. If it fits, it’s a C7 bulb. 


Both C7 and C9 bulbs are both quite small, respectively. If you’re shopping for lights for the purpose of decorating trees, outlining fences and rooflines or wrapping around banisters, it’s best to choose either or both of these bulb types as they’re small and versatile enough to serve as decor. 


Another answer to the question, “what is the difference between C7 and C9 bulbs” is wattage. A standard incandescent C7 bulb is up to four watts, while a similar incandescent C9 bulb runs up to 10 watts. Meanwhile, LED C7 and C9 bulbs typically require less electricity. Note however that they might not be as bright as incandescent bulbs.

Are C7 and C9 Bulbs Interchangeable?

The short answer is no. As discussed earlier, C7 and C9 bulbs require different bases—-E12 for the former and E17 for the latter.

C7 or C9 Bulbs: Which Ones to Use?

When deciding whether you should buy C7 or C9 bulbs, consider what you’ll be using them for and the size of the space you’ll be decorating. Will they be for indoor or outdoor use? Do you need them to be seen from a distance or only at close quarters? 


Since C7 bulbs are smaller, they’re best for illuminating centerpieces and mantles, lighting up wreaths and garlands as well as decorating indoor trees. They’re also great for dressing up apartment balconies, shrubs and outdoor displays like Nativity scenes. 


Meanwhile, C9 bulbs are smaller, making them ideal for large display installations as well as for general outdoor lighting for celebrations and holidays. Their large size is why you would commonly find C9 bulbs decorating commercial properties like malls as well as very large outdoor Christmas trees in town squares.


C7 and C9 bulbs come in a wide range of colors and textures, such as faceted and smooth. LED bulbs also have “warm” yellow-toned options as well as “bright” options that emit a white light. Some C7 and C9 bulbs blink and some even have a “flicker” effect that makes them look like real candles. To add to the candle-like effect, “flickering” C7 and C9 bulbs often have a tapered tip. 


For animated light shows, you should consider purchasing dimmable LED C7 and C9 bulbs. These require much less electricity than incandescent lights, which is helpful for keeping your power bill low even if you run the shows multiple times a day. 

C7 and C9 Bulbs: Important Considerations 

Whether you choose C7 or C9 bulbs, if you’re going to install them outdoors, it’s best to opt for lights that are labeled “certified waterproof.” Also you’re going to drape them around a tree or anything that is  potentially flammable, choose LED instead of incandescent. Unlike conventional lights, LED bulbs do not get hot to the touch. 


Other considerations are the style of decor you’re aiming to achieve. For instance, for a “winter wonderland” theme, you can purchase net lights that have already been strung together into shapes, like snowflakes and stars. All you need is to hang them up or drape them across or around trees and shrubbery. 


For a retro feel, you might want to get frosted LED C7 bulbs to outline the outside of your windows and doors. You can then use frosted LED C9 bulbs to illuminate the roofline of your home and your fences. 

Light Up Your Home With Quality C7 and C9 Bulbs

With C7 and C9 bulbs, you can turn your holiday lighting vision into reality. If you need high-quality bulbs, turn to Certified Lights. We offer a wide selection of lighting options, from waterproof LED bulbs to wire spools and connectors. Shop online today, or call 972-512-0000 to learn more. 

1 comment

  • Phyllis Griffin

    Want bright white light bulbs as well as bright red outlining our home. Which C9 bulb name should I order

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