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Bulb 101

June 4, 2020

Because there are so many bulbs to choose from, it is sometimes difficult to know where to begin. Knowing the socket size and the general shape of the bulb you are looking for is a good place to start.

Bulb Sockets

A bulb is often categorized by its socket size, indicated by the letter E followed by its diameter. The most common of these measurements are the E26 and the E12. While an E26 bulb has a diameter of 26mm, making it a standard for most light fixtures, an E12 has 12mm in diameter, making it the go-to for candelabras.

Common Bulb Shapes

Bulbs are also assigned a letter and number combination to indicate its shape and its corresponding shape size. Let’s take the standard bulb for instance. If you’re asked to think of a light bulb, odds are, the first thing that comes to mind is the A-19. The A indicates its shape (arbitrary) while the 19 indicates how many ⅛ inches are at its widest point.

Here are some of the most common bulb shapes you’ll find. And some of the most popular corresponding diameters.

  • Arbitrary (15,17,19, 20, 21, 23)
  • Candle (C6, C7, C9, C11, C13)
  • Tubular (T8, T12)
  • Globe (G25, G40)
  • Straight sided (ST18)
  • Bulged reflector (BR25, BR30, BR38, BR40)
  • Multifaceted reflector (MR8, MR11, MR16, MR20)
  • CFL Twist (T2 Coil, T3 Coil, T4 Coil)

Don’t know the wattage you need? Read more here.

The Return of the Edison

Edison Bulbs have been in vogue for the past few years, and as evidenced by the decor of every patio of every bar, the trend doesn’t appear to be slowing down. The style is an homage to the bulb’s earliest days, featuring recreated turn-of-the-century, glowing filaments in their original shapes, the most common being spiral, squirrel cage, and hairpin.  The glass is often hand blown and sometimes features an amber tint for an authentic, vintage-bulb experience.

Filament Types

  • Spiral Filament
  • "Squirrel Cage" Filament
  • Hairpin Filament

Oversized Bulbs

While the standard bulb sizes are most common, you may also come across unique, oversized bulbs that are more difficult to categorize. These often function as eye-catching statement pieces and come in a dynamic array of sizes and shapes to add a decorative touch to a simple pendant or sconce.

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