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Light Bulb Guide

Identify the type of light bulb you need with the simple light bulb guide below. We break down the bulb into parts to help you find the replacement bulb you need quickly and easily.

1)  Determine the type of bulb

There are a large variety of bulb types. The most common types include incandescent, halogen, fluorescent, compact fluorescent, xenon, and metal halide.

2) Determine the shape and size of the bulb

Bulbs are usually identified by a letter, then a number. (e.g. A19, PAR30, etc.) The beginning letter, or set of letters, indicates the shape of the bulb. The following numbers indicate the diameter of the bulb, measured in eighths of an inch. For example, an MR16 would have a 2" diameter and a PAR30 would have a 3.75" diameter.

Light Bulb Shapes & Sizes

3) Determine the base of the bulb

The base of the bulb connects to the socket. View different types of commonly used bases below.

Light Bulb Bases

4) Determine the options

The options of the light bulb, which are the color temperature and wattage, can be identified from the ordering code of the bulb. Learn how to decipher the ordering code on your light bulb using the chart below.

Click view chart on deciphering light bulb ordering codes.


40 = Wattage
G25 = Globe, 25 eighths of an inch diameter (3.125")
CL = Clear
3 = Voltage (130V)


40 = Wattage
E = E26 Base (Standard)
F = Flame
C = Clear
3 = Voltage (130V)



EXN = ANSI code for 50W MR16 40" Flood
L = Lensed


H = Halogen
75 = Wattage
PAR30 = Parabolic Aluminum Reflector, 30 eighths of an inch (3.75")
NF = Narrow Flood
3 = Voltage (130V)



F = Fluorescent
32 = Wattage
T8 = Tube, 8 eighths of an inch diameter (1")
= 80CRI
35 = Color Temperature (3500K)
HL = High Lumen


Compact Fluorescent


CF = Compact Fluorescent
13 = Wattage
WW = Color Temperature Warm White
GU24 = Twist and Lock Base (24mm)
DM = Dimmable


CF = Compact Fluorescent
18 = Wattage
T = Triple Tube
8 = 80CRI
41 = Color Temperature (4100K)
E = Electronic 4-Pin

High Intensity Discharge (HID)


MH = Metal Halide
24 = Wattage
PAR38 = Parabolic Aluminum Reflector, 38 eighths of an inch (4.75")
NFL = Narrow Flood
SB = Self Ballasted


M = Metal Halide
70 = Wattage
U = Universal Burn Position
MED = E26 Base (Medium Base, Standard)
O = Open Fixtures



JC = JC Bi-Pin
5 = Wattage
XE = Xenon
12 = Voltage (120V)


KX = Krypton Xenon
40 = Wattage
CL = Clear
E12 = E12 Base (Candelabra)

5) Contact the fixture manufacture

If you still have difficulty finding the replacement bulb for your fixture, you can contact the manufacturer directly. Provide them with the brand and model of your fixture.

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