E26 / E27 Base
The standard Edison screw base used in most household lamps and fixtures. E26 (26mm) is the North American version, E27 (27mm) is the European equivalent.
E26 and E27 are the world's most common light bulb bases — the classic screw-in fitting invented by Thomas Edison. The "E" stands for Edison, and the number is the thread diameter in millimeters. E26 at 26mm is the standard in the US and Canada, while E27 at 27mm dominates in Europe, South America, the Middle East, and much of Asia.
Also called the "medium base" or "standard base," E26/E27 is used on A19, A21, BR30, PAR38, and many other bulb shapes. If a fixture accepts a screw-in bulb and it's not a small candelabra socket, it's almost certainly one of these two.
The 1mm diameter difference means bulbs will often physically fit in either socket. However, they're designed for different voltages — E26 for 120V, E27 for 220-240V. Modern LED bulbs often include wide-range drivers (100-240V) and are sold as "E26/E27 compatible," working safely in either socket. Incandescent and halogen bulbs are voltage-specific and should not be swapped between the two.
Specifications
| E26 diameter | 26mm (North America, 120V) |
| E27 diameter | 27mm (Europe, Asia, 220-240V) |
| Type | Edison screw (medium) |
| Also known as | Medium base, standard base |
Related Terms
- E12 Base
A smaller 12mm Edison screw base used in decorative fixtures like chandeliers, wall sconces, and night lights.
- B22 Base
A bayonet cap base with a 22mm diameter, standard in the UK, Australia, and parts of Asia. Push-and-twist to lock into the socket.
- A19 Bulb
The standard household light bulb shape — a pear-shaped bulb 2.375 inches in diameter, used in most lamps and fixtures.
Mentioned in
What Is An E26 Bulb?
A19 and E26 aren't two names for the same thing — one describes the bulb's shape, the other its base, measured in completely different units on the same bulb.
How Do I Know What Base My Light Bulb Is?
E26 isn't just a label — it describes the bulb: E for Edison, 26 for the shell diameter in millimeters. The same logic unlocks every other base code too.
What Light Bulbs Are Best For Chandeliers?
Chandeliers use a smaller E12 candelabra screw base, not the E26 in your floor lamp — and buying the wrong size is the single most common chandelier bulb mistake.