Light bulbs | light bulb shape & socket/base types | LED Lights | CFLs
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Lighting lamps and light bulbs are described by a shape, diameter, length and screw type designation. This normally is in the form of letter(s) followed by a number followed by an optional letter.
A standard 60-100 watt household bulb is an A19 A = Arbitrary Shape (see below); 19 = 19/8th in. [2 3/8 inch] in diameter [A metric A60 (60 mm in diameter) is the equivalent], with an E26 screw base. bulb shapes
Source: EagleLight

LED Lights

Fluorescent tube bulbs
Circular fluorescent light bulbs differ in many ways and sometimes come with manufacture-only specifics. Bulbs range from 5"-12" in diameter.
florescent lights T5 T6 T8 T12 T10 G13 G5

Sockets and base type:
'Exx', 'E' stands for 'Edison' and 'xx' refers to the diameter in millimeters as measured across the peaks of the thread on the base (male)

E10, E11, E12, E14, E17, E26 (Standard Bulb), E27, E36, E39, BA15, SC,
GU10, GU24, G4, G5.3, GY6.35, GU8 GY8, G9, G12
 E10, E11, E12, E14, E17, E26, E27, E36, E39, BA15, SC, GU10, GU24, G4, G5.3, GY6.35, GU8 GY8, G9, G12   
LED light bulb sockets and bases are manufactured to the same standards as
halogen, incandescent and other traditional lights.
Edison Screw-in (ES)
Candelabra: E12 (diameter of 12 mm) [0.47"]
Intermediate: E17 (diameter of 17 mm) [0.67"]
Medium or Standard: E26 (diameter of 26 mm [1.02"]
Mogul: E39 (diameter of 39 mm) [1.54"]

More at
EnergyStar categorizes bulbs as:
Omnidirectional: A, BT, P, PS, S and T 
Decorative: B, BA, C, CA, DC, F, G
Directional: R, BR, ER, MR and PAR 

 LED Light Bulb Base Types |
and LED Light Bulb Base Types |
A - Arbitrary shaped bulbs (standard household bulbs) A15, A19, A21, A23
Diameter in.
1 7/8
2 3/8
2 5/8
2 7/8
PAR - Parabolic Anodized Reflector bulb PAR16, PAR20, PAR30, PAR36, PAR38, PAR46
Diameter in.
2 1/2
2 1/2
3 3/4
4 1/2
4 3/4
5 3/4
Source: EagleLight

BR (for bulged reflector) bulbs are lamps with "wide flood" beam angles, which means that they provide more than a 45 degree angle when lighting an area.

Multi Faceted Reflector (MR) Halogen and LED

Beam Angle (spot/flood)
Code Typical MR16 Typical PAR Description
VNSP <7 degree s<15 degrees Very narrow spot
NSP 5-15 degrees 15-30 degrees Narrow spot
SP 16-22 degrees 30-60 degrees Spot
NFL 23-32 degrees 60-90 degrees Narrow flood
FL 32-45 degrees 90-120 degrees Flood
WFL 45-60 degrees 120-160 degrees Wide flood
VWFL 60+ degrees >160 degrees Very wide flood
Source: LED Beam Angle |

B10.5, B13, BA9, BA9.5 Candelabra bulbs are sometimes listed as B and BA and C. Bases are typically E12.

ACEC - Advisory Committee on Electromagnetic Compatibility (part of IEC)
ES - Edison Screw
IEC - International Electrotechnical Commission (or CEI in French) - Sets standards
MES - Medium Edison Screw

Edison screw - Wikipedia
LED Light Bulb Shapes and Sizes - Lamp size reference
Light Bulb Shapes and Sizes | LED Lamps Education | LED Lighting
Light Bulbs | Incandescent Shapes |
LED Lighting |
Halogen Lamps - MR11 and MR16 - Focused Ellipsoidal Dichroic Reflectors | ILT
S-6 Shape Bulb Identification - YouTube

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last updated 12 Nov 2013