How it connects
The bulb's male rounded (knuckle) thread screws into the socket shell; the shell is one contact (neutral) and the bulb's insulated base tip presses on a spring center contact (hot). No seal.
Male and female halves
The socket/lamp holder is female; the bulb base is male. This connection is the female socket.
Usually connects to
- E26 medium screw-base incandescent, LED, CFL or halogen bulb
- E27 lamp (usually physically interchangeable)
- E26 screw-in socket adapter, bulb adapter or plug
Common sizes
- E26: nominal 26 mm thread diameter, 7 TPI, about 3.629–3.63 mm pitch; typical ratings 120/250 V up to 660 W.
- Related Edison sizes: E5, E10, E11, E12 candelabra, E14 SES, E17 intermediate, E27 European and E39/E40 mogul. E26/E27 bulbs generally interchange in practice.
Where it is used
residential lighting fixtures; commercial lighting; commercial fixturesoutdoor wall lanternstable and pendant lampsappliancesgarage door opener light socketsluminaireslamps and light fixturesrange hoods and exhaust fans with lights
Variations
- E26 medium
- E27
- Related E12 candelabra, E14 small, E17 intermediate and E39/E40 mogul
- Keyless, pull-chain, turn-knob/switched or three-way socket
- Porcelain, phenolic or brass shell
- External shade-ring thread
How to recognise it
A cylindrical cup (porcelain, plastic or brass) about 26-27 mm inside with a coarse rounded thread formed in a metal shell, and a brass tab/spring contact at the bottom center. Usually marked E26 or E27 and 660W/250V. A threaded hole or 1/8 IPS nipple at the back for mounting.
Often confused with
| Confused with | How to tell them apart |
|---|---|
| Bayonet cap socket (B22, BA15) | Bayonet has a smooth bore with two J-slots and push-and-twist pins; Edison has a continuous helical thread. |
| GU10 / GU24 twist-lock socket | GU types have pin holes in a flat face; Edison is a deep threaded cup. |
| Socket shade-ring thread / 1/8 IPS nipple thread | The outer thread on the socket body (for shade rings) and the 1/8 IPS threaded nipple at the back are mounting threads, not the bulb interface. |
| E27 lamp socket | E27 is the 27 mm European/international standard (pitch 3.62 mm) used at 230V mains; E26 is 26 mm nominal for 120V regions. Bases can often physically screw into each other, but E26 sockets have different contact reach and creepage/clearance. |
| E12 socket | E12 is candelabra size with a much smaller 12 mm diameter thread. |
Also called
E26 lamp holder; E27 lamp holdermedium base socket; Standard base lamp socketES lampholderscrew-in light socket; Medium Edison Screw socketE26 socketE26 lampholderMES socketstandard bulb socket
Good to know
The bulb socket and any external shade-ring thread are separate connections. Additional standard references: IEC 60061-2 (sheet 7005-21A).
Related connections
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