Light Bulb Socket Sizes Chart

By the end, you’ll see how much use a light bulb socket types chart can be to determine your bulb holder sizes.

Thomas Edison invented the Edison screw fitting, a screw mount mechanism for light bulbs, in 1909. Although bayonet sockets and a variety of bulb shapes are available, they all perform identical functions.

Edison screw lamp bases and fittings are now produced to international standards and used for general and specialty lamps. A threaded metal base screws into a matched socket to hold the bulb. (Read Socket Sizes Chart)

Bulbs are now widely used in various applications, including Christmas lights, outdoor string decorative lights, night lamps, indicator lights, and many other typical applications.

However, it is the screw bases that vary in size and thread, not the bulb shapes, whether pear-shaped or spherical globe-shaped.

Our guide will teach you everything you need to know about the standard light bulb socket size for your pendant lights or general lighting in your home. By the end, you’ll understand how valuable a light bulb socket types chart is for determining bulb holder sizes.

Are E26 and E27 the Same?

The minimum distances between the bottom live contact and the screw threads change between E26 and E27. The reason is that the E26 and E27 are designed for differing line voltage levels – 120V AC and 240V AC.

The diameter of the E26 is 26 mm, while the E27 is 27 mm. Therefore, an E26 bulb can be used in an E27 base, and an E27 bulb may be used in an E26 base without difficulty.

E26 and E27 lamp bases have the exact diameter specifications built to the widely approved IEC light bulb socket standards of 26.05 mm to 26.45 mm.

You will usually always find that E26 and E27 lamp bases are mechanically interchangeable, meaning that an E26 bulb will fit into an E27 socket and vice versa. However, as a bulb fits and works doesn’t mean your lamp complies with electrical safety standards.

How Do I Know What Size Light Bulb Socket I Have?

There are many light bulb base sizes available.

• C7 / E12 / Candelabra Base socket size Bulbs: Used on chandelier-type fixtures or decorative lighting.
• C9 / E17 / Intermediate Base Bulbs: Commonly known as the old Christmas light bulb size.
• Medium / E26 Bulbs (E27 in Europe): Your standard household bulb size.

The following provides the dimensions of a bulb socket which is helpful if you’re trying to match the socket size of a bulb you already have.

For more explanation of the light bulb base sizes, you can check letter-number references (E12, E17, and E26) to help with the bulbs base style and size.

The first letter designates the shape or form of the base, and the number represents the width of the base (normally in millimeters). For example, the 11S14 bulb has an E26 base, and the “E” refers to an Edison screw-in, and the 26 is the 26 mm base width.

Light Bulb Shapes are like identifying the base size, and light bulbs use a letter-number reference for the shape and size of a light bulb. (Find the Best Battery Operated Lights)

Letters refer to shape, and numbers refer to sizes.

• A (Arbitrary): Resembles the standard household bulb.
• C (Conic): Typically referred to as a traditional Christmas tree bulb.
• G (Globe): Round or circular.
• S (Sign): Straight-sided and traditionally used in signs.
• ST (Straight Tapered): Most often seen in vintage, Edison-style bulbs.
• T (Tubular): Tall narrow tube-shape and also used in vintage, Edison-style bulbs.

What Are the Different Light Bulb Socket Sizes?

The Exx number refers to the diameter in millimeters, even inside the USA, where eighths of an inch measure bulb glass. You can find four sizes of screw-in sockets used for line-voltage lamps:

• Candelabra: E12 (diameter of 12 mm): E12 is the smaller “miniature Edison screw mes” base used for nightlight bulbs and decorative light bulbs used in chandeliers and bathroom mirrors.
• Intermediate: E17 (diameter of 17 mm): E17 (intermediate Edison screw ies) sits between two sizes. It’s often used in desk lamps and appliance bulbs, although not very common.
• Medium or Standard: E26 (diameter of 26 mm): E26 is the size of most light bulbs in the US.
• Mogul: E39 (diameter of 39 mm): The large E39 “mogul” base is used for street lights and high-wattage lamps.

Edison Light Socket Sizes Chart

Here is the light bulb base size chart for Edison light fixture sockets.

Size	Name	Base major diameter (thread external)	Usage Scenario	Notes
E5	Lilliput Edison Screw (LES)	5 mm	Decorative, Indicators	Another name is "Midget"
E10	Miniature Edison Screw (MES)	10 mm	Bicycle Lights, Flashlights	Also called "Miniature Screw"
E11	Mini-Candelabra Edison Screw (mini-can)	11 mm	120v Halogen Mini Candelabra
E12	Candelabra Edison Screw (CES)	12 mm	120v Candelabra, Night Lamp	It can be called “Candelabra”, C7 Common US Socket
E14	Small Edison Screw (SES)	14 mm	230v Candelabra, Chandelier, Night Lamp, Pendant Light
E17	Intermediate Edison Screw (IES)	17 mm	120v Appliances	Another name is "Intermediate", C9
E26	Edison Screw (ES or MES)	26 mm	Standard 120v Lights	AKA "Medium", Most Common US Socket
E27	Edison Screw (ES)	27 mm	Standard 230v Lights	AKA "European Intermediate"
E29	Admedium Edison Screw (ES)	39 mm	Specific Applications such as UV Spotlight Lamps
E39	Sing-contact Goliath Edison Screw (GES)	40 mm	120v 250+ W Industrial	Known as "Mogul", Common US Socket
E40	Goliath Edison Screw (GES)		230v 250+ W Industrial

Bi-Pin Socket Sizes Bulb Base Chart

Bi-Pin bulbs are often used in tubes rather than the more traditional bulb shape.

Fitting Designation	Pin Spacing	Pin Diameter	Common Usage
G4/GY4	4mm	65 - .75mm	5-20w Small Halogen Quartz Capsules
GU4/GZ4	4mm	.95 - 1.05mm	MR8 And MR11
G5	5mm	N/A	T4 Or T5 Fluorescent Bulbs
G5.3	5.33mm	1.47 - 1.65mm
GU5.3/GX5.3	5.33mm	1.45 - 1.60mm	20-50w Small Halogen, (Like MR16)
GY5.3	5.33mm	flat pins
G6.35/GX6.35/GZ6.35	6.35mm	0.95 - 1.05mm
GY6.35	6.35mm	1.2 - 1.3mm	Halogen Used In Landscape Lighting
G8	8mm	N/A	35-100w Halogen
GY8.6	8.6mm	N/A	100w Or Below Halogen
G9	9mm	N/A	120v Or 230v Halogen And LED Lamps
G9.5	9.5mm	3.10 - 3.25mm	Theater Use
GU10	10mm	N/A	35-50w MR16 Halogen; Compact Fluorescent And LED Lamps
GZ10	10mm	N/A	Adds Dichroic Filter To GU10; May Use GU10 Bulbs
G12	12mm	2.35mm	Single-End Metal Halide Lamps
G13	13mm	2.35mm	T8/10/12 Fluorescent Tubes
GX16d	16mm	N/A	Theatrical PAR Lamps
G23	23mm	2mm	Fluorescent PL Lamps In Recessed Fixtures
GU24	24mm	N/A	Twist-Lock (Self-Ballasted Compact Fluorescent)
G38	38mm	11.1mm	High-Powered Theatrical Lamps
GX53	53mm	N/A	Twist-Lock (Under-Cabinet Compact Fluorescent; Or LED)
GX70	70mm	N/A	Twist-Lock (Puck-Shaped Compact Fluorescent And LED)

What Size is A Standard Light Bulb Fitting?

The screw medium E26 has the most common medium base socket dimensions of any bulb base in the United States. Most incandescent, nostalgic LED, CFL, and halogen light bulbs contain it. The Candelabra E12 base, which is used for smaller ornamental incandescent/nostalgic bulbs, is the second most common bulb base.

LED bulbs are changing bulb selection; however, they still employ the same medium base socket size, although the bulb functions differently.

When picking an LED bulb, it’s essential to consider the light output. It’s measured in lumens (light output) when everything used to be measured in wattage in the early days.

To replace existing incandescent bulbs, screw base bulbs with the recognizable Edison screw socket are used. Replace your old incandescent bulb with your new CFL to save money on energy.

Pin-base CFLs feature two or four pins on their compact plastic bases and are used with separate ballasts in fixtures designed for pin-base CFLs.

The GU24 socket and base system should replace the Edison screw ES standard socket and base in energy-efficient lighting fixtures in order to comply with the most recent ENERGY STAR criteria. GU24 bulbs are used in fixtures that avoid backward compatibility with screw base bulbs, resulting in improved energy efficiency.

Bulb Type	Application	IEC 60061-1 Standard Sheet
E5	Indicator Lights, Decorative Lights	7004-25[11] (lilliput Edison screw les)
E10	Flashlights, Bicycle Lights	7004-22
E11	120 V Halogen Mini-Candelabra	(7004-6-1)
E12	120 V Mini Candelabra Edison screw/Night Lamp	7004-28
E14	230 V Candelabra/Chandelier, Night Lamps, And Some Pendant Lights.	7004-23 (candelabra Edison screw ces)
E17	120 V Appliance / Outdoor Christmas	7004-26
E26	Standard 120 V Lamps	7004-21A-2
E27	Standard 230 V Lamps	7004-21
E39	120 V 250+ W Industrial	7004-24-A1
E40	230 V 250+ W Industrial	7004-24

You can find many screw bases and it can appear daunting, to begin with. However, when shopping for bulbs, it is much more straightforward than checking if you have a Small Edison screw SES or an Edison screw ES standard bulb. (Find the Best Rechargeable LED Flashlight)

The type of fixture dictates the base types by the size. In the USA, the base type can vary in size, and it isn’t too challenging to find the right bulb for your candelabra night lamp or if you thread external lights around your garden.