Labeling on Incandescent Light Bulbs

Identifying Info on Light Bulbs



12 Volt/1.2 Watts with a 3/8" Tubular bulb (T3) and a Wedge Base



12 Volt/50 Watts with a 1/2" Tubular (T4)  JC style bulb (XJC) and a bi-pin base with flattened pins spaced 6.35mm apart (GY6.35)

JC35 BA15D

12V 35W

12 Volt/35 Watts with a 1/2" Tubular bulb (T4) and a Automotive Bayonet base (BA) with double contacts (D or DC) spaced 15mm apart.

40W 120V

120 Volt/40 watt that is 19 eighths wide A19  bulb (2.375") and a medium screw base or Edison base

Capsylite Par30/50W 120V/FLOOD


120 Volt/50 watt parabolic aluminized reflector (PAR), sealed beam flood (wide angle) that is 30 eighth inches across or 3.75".
EXN-SILVER 12V 50W 38°

12 Volt/50 watt Mirrored Reflector that is 16 (MR-16) eighths wide (2") with a pre-focused pattern of 38 degrees with silver casing.

I.D. Code on the Lamp

Identifying information for light bulbs can generally be found in two places; on the packaging it comes in and on the light bulb itself. Let's look at the light bulb first.

On most light bulbs, although not required, the wattage and the supply voltage should be the minimum information supplied on the light bulb itself. This information is usually stamped on the base unless the base is so small it won't permit it or the base doesn't have a smooth surface to get a good print, as in the case of the T3 wedge. If the base is composed of metal, many times the lamp information is imprinted in the metal. This is a nice feature since with time and wear, inked information will, most likely, be unreadable.

There is no real standard for labeling printed on the lamp, so you may see the manufacturer's name and item number along with (and sometimes without) voltage, wattage and configuration information. Since there is no standard, you can pick up some information from the printed label by knowing what you are looking for. For instance, you may see a number that looks like a lighting code (3EFC FLICKER 3W 120V) but it doesn't match what you expect to see. Since the lamp is 120 volt, the 3 watt designation seems too low and the EFC designation doesn't fit the pattern for bulb shape. You should assume this is, most likely, a manufacturer's model number. When you look up this number on the manufacturer's website, you find it is a 3W LED that has a CA11 bulb type with a plate filament that mimics a burning flame.

The identification code for mirrored reflector (MR) lamps is a bit different. At this time there are three sizes of MR lamps that are primarily used in a retail setting. MR-8 (1"), MR-11(1 3/8") and MR-16 (2") are identified based on a 3 letter ANSI code indicating the lamp's wattage, voltage, base type and distribution pattern. Since the MR lamps are so widely used, manufacturers adopted a standard where lamps with a specific code have the same specifications no matter the manufacturer. This standard established by the American National Standards Institute (ANSI) is the one primarily used in the industry.

It's very easy to get really confused when you go online to find a replacement lamp because there will be other modifiers associated with the identification code on a lamp. There will be add-ons like FG for a glass covering the inside of a MR lamp, different lamp life, etc. Just remember you are looking for the parts of the code you recognize, all the other letters may or may not have relevance to replacing the lamp that burned out.

If you can't find any printed information on the lamp you will have to refer to the charts on bases, bulbs and filaments to try and identify the lamp required to replace it. As an alternative, you can fill out our Light Bulb Identification Form and we will try to help you identify your lamp.

Satco provides an extensive catalog with ANSI identification codes, size, shape, base type and the characteristics associated with each. 

Satco Catalog

I.D. Code on the Packaging

The U.S. Federal Trade Commission now requires manufacturers of incandescent, compact fluorescent and LED light bulbs to use new labeling on consumer packaging to help consumers choose the most efficient bulbs for their needs.

While watt measurements are familiar to consumers, the rising popularity of energy saving technologies including compact fluorescents and LED, make comparing bulbs with old technology and new technology an unfamiliar concept. The new standard for comparing bulbs of varying technologies is based on the amount of light or brightness produced by the bulb. 

For the first time, a "Lighting Facts" label on the side or back of the package emphasizes a bulb's brightness as measured in lumens, rather than a measurement of watts.The new front-of-package labels also includes the estimated yearly energy cost for the particular type of bulb.

The back of each package must have a “Lighting Facts” label modeled after the “Nutrition Facts” label that is currently on food packages.

The Lighting Facts label provides information about: Brightness, as measured in lumens (not watts)

* Estimated yearly energy cost

* Life expectancy

* Light appearance (for example, “warm” or “cool”)

* Energy used (as measured in watts)

* Whether the bulb contains mercury