What is the difference between a C7 and a C9 Light Bulb?

What is the difference between a C7 and a C9 Light Bulb?  Lee Display can answer your question and help make your next purchase less stressful!

We get the same questions over and over again about what the difference is between each bulb, what will fit with what socket, how will I know which bulb fits with which socket.  And it can be difficult to understand the subtle difference between each type of light bulb, especially when you're only buying them once a year for the holidays.  

So, we'll focus on what's most typically found for anyone searching on Amazon or through Lee Display's online store.  


The Main Difference:  Size!

C7 Light Bulbs:

c7 light bulb dimensions and size lee display what's the difference blog post

  • 2.125in total length (with base included)
  • 1.5in long bulb
  • 0.825in diameter
  • E12 base

 C9 Light Bulbs:

c9 light bulb dimensions c7 c9 blog post page

  • 2.875in long total (with base included)
  • 2in long bulb
  • 1.125in diameter
  • E17 base


C7 Bulbs are much smaller than the larger C9 Bulb.  C-9's are longer, wider, and fit into a bigger socket. 

As you can see from the photographs above, the C7 Bulb is usually 2-1/8in in length and 7/8in in width.  In comparison, the C9 Bulb measures 2-7/8in in length and 1-1/8in in width.  Since the C7 and C9 bulbs are so difference in size, they require a difference base and socket.

c9 solid ceramic light bulb fitting into a wrong socket lee display blog post what's the difference

You can't fit a C9 Bulb into a C7 Socket!

Typically, C7 bulbs are made on an E12 sized base.  C9 bulbs are made on an E17 sized base.  They are so often manufactured in-line together that the terms for C7/E12 and C9/E17 are interchangeably misused.  C7/C9 refers to the size and shape of the light bulb.  While E12/E17 refers to the size of the brass metal base used to screw in to the corresponding socket.  For C7 & C9 Light Bulbs; the size of the base is either E12 or E17.  The higher the number; the larger the size of the base.


The Decorative Difference:  Style

Each of these types of bulbs are typically referred to as Candelabra bulbs.  They get the name because they look like little candles when lit at night. 

Each size (C7 or C9) come in varying colors and styles; from Solid Colors or Transparent colored to Twinkle Bulbs and/or Steady.  

  • Twinkling bulbs have a filament inside the bulb that when heated up by the socket, breaks apart and causes the illusion of a blinking/flashing/twinkling light bulb.
  • Steady Bulbs stay on continuously while plugged in.  No flashing on and off.
  • Transparent Light Bulbs are made from glass and dipped in paint for color.  Bulbs that are dipped 3 times or more, have a much deeper and darker color hue when lit.
  • Solid Colored Light Bulbs are made from ceramic and coated in colored paint.  While they're opaque while turned off, when turned on the light emits thru the coating of paint and looks a bit more pastel glowing.


The Most Important Difference:  Base Size

So you're almost ready to purchase a new box of lights to replace the old ones that have burnt out, but you're still wondering if the bulbs will screw in and fit your sockets.  Here's the most important part:

How to find the size of your socket:  Measure the width of the socket

Not every set of patio cords will have "E-12" or "E-17" printed on the wiring and you may have lost the tags that would've included this information.  So you're left with having to measure the size of the socket.  But it's important to know, there's not much of a difference between the length of a C7 Socket to the length of a C9 Socket.  

The Most Important Difference is the width:

C7 Sockets Measure:  .55in width

C9 Sockets Measure:  .75in width


Ready to Buy?  Lee Display offers a wide variety of Candelabra bulbs in different sizes and colors for any holiday occasion.  

Shop for C-7 Bulbs Here

c7 light bulbs on sale lee display redirect from what's the difference blog post page

And Purchase C7 Cords and Sockets Here

C7 Patio String Cords from difference of c7 c9 blog post

Shop for C-9 Bulbs Here

c9 Light Bulbs shop collection redirect from what's the difference blog post


And Purchase your C9 Cords and Sockets Here

c9 patio string cords and sockets redirect from blog post



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