Chris Primous is the Vice President of OEM sales and Industry Relations at MaxLite. He is a recognized energy-efficient lighting industry expert, educator, and champion for the lighting manufacturing industry with programs such as ENERGY STAR, California Title 24 and Title 20.
What do all of these letters and numbers mean in bulb shapes? These are confusing.
These letters are lighting industry terms that represent the SHAPE and SIZE of the lamp. The first one or two letters represent the shape of the bulb and follow a national standard naming convention created by ANSI (American National Standards Institute). Common types are below.
The numbers (which sometimes follow a dash "-" after the aforementioned letters), represent the diameter at the widest part of the bulb, in eighths of an inch. For example, A-19 is a A-shaped lamp (as described below), which is 19/8" diameter at its widest point. Note that each manufacturer selects how they want to designate their bulb shape, and some of the ANSI shape descriptors are quite similar. Therefore, it is not unusual for similar-looking bulbs from two different manufacturers to describe the shape of their bulbs quite differently.
A - Arbitrary / Appliance - Standard household incandescent light bulb shape
B - Bulged or Bullet tip
BT - Blown Tubular bulb shape
BR - Short reflector style light bulb;
C - Candle or Conical bulb shape
CP - Crystalline Pear bulb shape
E - Ellipsoidal bulb shape
ER - Ellipsoidal reflector light bulb shape
F - Flame style candelabra bulb shape
G - Globe bulb or circular bulb
HK - Hexagonal Candle
K -Krypton or narrow reflector light bulb shape
MR - Multi-faceted reflector
P - Pear bulb shape
PAR - Parabolic Aluminized Reflector (PAR) lamp
PS - Elongated standard incandescent bulb
R - Reflector light bulb style
S - Strait Sided bulb style
T - Tube lamp shape
ST- Straight Tubular
