Light Bulb Fitting Guide: Light Bulb Types and Shapes

The base of the light bulb is important because it determines what type of light fixture the bulb can be connected to. A lot of the common bulbs will have a screw or Edison base. This type of base is easy to use as it is to install. But if you were going to try to install a pin based light bulb that was designed for a screw base you won’t be able to connect them.

In addition, just like the base the bulb type can help you determine which light will work best for your fixture. An A19, for example, would be perfect for the office or home but would not do so well when you are trying to light a larger space like a warehouse. So knowing the type of a bulb can help you get the type of lighting that you want. For light bulb connector tyes and bulb bases, check out this blog!

Bulb Types and Bases

Which Light Bulb Do I Need?

Bulb Type:
  • Has four pins that are linear across the bottom of the base
  • External ballast gives you flexibility in application
  • If incorrectly installed the life of the bulb will be shortened
  • Hotels
  • Restaurant
  • Retail stores
  • Warehouse
  • Offices
A19 and A21 A19 bulb type
  • Also known as general service bulbs
  • 'A' is for the way that it's shaped like an 'A'
  • The number is the diameter of the bulb in millimeters
  • Directional light bulbs
  • Has a 180 degree beam angle so no light is wasted
  • Recessed lighting
  • Table lamps
B10                                                      B10 bulb type
  • The 'B' stand for blunt rather than flame tip
  • Can be used with a candelabra or medium base
  • Chandeliers
  • Decorative lighting
  • 'BR' stands for Bulge Reflector 
  • The number following 'BR' refers to the size of the bulb in 1/8 inches 20/8, 30/8, and 40/8 inches
  • Has a reflective coating found inside the bulb
  • BR40 is used for high ceiling and has higher wattages
  • BR30 bulbs are great for low ceilings
  • Ambient lighting
  • Hallways
  • Office space
CFL CFL bulb type
  • Also known as a compact fluorescent light
  • Made to replace incandescent bulbs
  • Contains mercury making it difficult to dispose of
  • Household lighting
  • Office 
  • Kitchen
C7                                                          C7 bulb type
  • Has a candelabra or E12 base
  • TYpically used in decorative lighting
  • Decorative lighting
  • Chandeliers
G25                                                      G25 bulb type
  • 'G' refers to the round globe shape 
  • The diameter of the bulb is 1/8 of an inch relative to the number following (ex: 25/8 = 3 1/8 inches)
G30, G40, G50                                          G30 bulb base
  • 'G' means that the shape of the bulb is like a globe
  • The number following 'G' is the diameter of the bulb in millimeters 
  • The base is usually a C7
  • Commonly used as string lights
  • Event decorating
  • Weddings
  • Patios
  • Cafes
  • Bistros
  • Clubs
Integrated LED Integrated LED bulb
  • Outdoor light fixture
  • Simplifies lighting installation
  • Maintenance and lighting improvement can be difficult
  • Any outdoor light fixutres
JC                                                           JC bulb type
  • Low voltage halogen bulb
  • Capsule-shaped
  • 2 pins at the base
  • Bulb can be damaged by oils from the skin and should not be touched bare handed
  • Under counter
  • Desk lamps
  • Accent lighting
LED Track Lights                                       LED track light bulb
  • Is a versatile light
  • Used on a continuous track device which has electrical conductors
  • Directional lighting
  • Spot lighting
MR16                                                   MR16 bulb type
  • 'MR' stand for mirrored reflector
  • The number that follow refers to the diameter that is 16/8 inches or 2 inches 
  • Has two pins on the bottom
  • Is a push fit type of bulb due to its installation
  • Track lighting
  • Display lighting
MR11                                                     MR11 bulb type
  • Has two sharp pins on the bottom
  • Classified as a push fit bulb by its form of installation
  • 12 volt lamp that requires a transformer
  • The width of the bulb is 35 millimeters
  • Bathrooms
  • Emergency lighting
  • Corridor lighting
PL                                                        PL bulb type
  • Made for retrofitting CFL plugins
  • Allow horizontal or vertical mounting
  • Generally used in commercial buildings
  • Downlights
  • Porch sconces
  • Decorative lighting
PAR                                                      PAR bulb type
  • 'PAR' stands for parabolic aluminum reflector
  • Has a sharp focused light
  • Durable and strong light outputs
  • Locomotive headlamps
  • Aircraft landing lights
  • Recessed lighting
R20                                                        R20 bulb type
  • 'R' stands for reflector
  • The number is the diameter of the lamp in terms of 1/8 of an inch (ex: 20/8 = 2.5 inches)
  • Track rings
  • Recessed can
  • Indoor spotlight
  • Outdoor spotlight
  • Flood fixtures
S14, ST18, ST19                                           S14 bulb type
  • Comes in different colors
  • Vintage type of lighting
  • 'S' stand for straight side
  • The number refers to 1/8 of an inch of the bulbs diameter (ex: 14/8 = 1 3/4 inches)
  • Amusement parks
  • Hotels
  • Casinos
  • Theatrical lighting
T12                                                         T12 bulb type
  • 'T' means tubular shaped
  • The number refers to 1/8 of an inch of the bulbs diameter (ex: 12/8 = 1.5 inches)
  • Household lighting
  • Office area
  • Kitchens
T10                                                       T10 bulb type
  • 'T' refers to its tubular shape
  • The number that follows 'T' is the 1/8 of an inch for the lamps diameter (ex: 10/8 = 1 1/4 inches)
  • Banker lamps
  • Podium lights
  • 'T' refers to the tubular shape of the bulb
  • The number following 'T' refers to the diameter of the bulb which is 1/8 inches (ex: 8/8 = 1 inch)
  • More efficient in climate controlled areas
  • It won't shine as well with ceilings higher than 8 feet
  • Garages 
  • Storage areas
  • Fabrication floors
  • Designed to replace linear fluorescent tubes
  • 'T' means that it has a tubular shape
  • The number following refers to the diameter that is 1/8 of an inch (ex: 5/8 = 5/8 inches)
  • Linear fixtures 
  • Strip lights
  • Shop lights
  • Troffers
  • Under cabinet lighting
U Tube                                                   U Tube bulb type
  • A 'U' shaped bulb
  • Produces light the same way as a T5 and T8 through electronic circuits
  • House lighting
  • Offices
  • Kitchens
Bulb Shapes

The type of light bulb that you choose can greatly affect the ambience and the beam angle of your setting. Depending on the type of setting that you are working with you may want a type of ambience that promotes production or one that makes people feel comfortable when they are there. Make your next trip to the electrical supply store easy and quick. Do you know what type of bulb and base you want? We are sure you do now!

Will Owen
Will Owen

B.A. in English from Kennesaw State University. Will takes what he's learned and writes about all sorts of things from artists to electrical supplies and LED light systems. You name it and he can probably write about it.

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