E26 Vs E27 Bulbs - Interchangeable? Not Necessarily!

SHOP BY APPLICATION SHOP BY APPLICATION

• RESIDENTIAL
• FILM & PHOTO
• HORTICULTURE
• AQUARIUM
• ARTWORK
• JEWELRY
• HUMAN CENTRIC
• AVIAN
• ULTRAVIOLET
• ABSOLUTE SERIES

SHOP BY PRODUCT TYPE SHOP BY PRODUCT TYPE

• A-Series Bulbs
• Decorative Bulbs
• LED BR30 Lamps
• LED Tubes
• LED-Ready T8 Fixtures
• LED Linear Fixtures
• LED Shop Lights
• LED Flex Strips
• LED Strip Accessories
• LED Modules
• Power & Dimmers

SHOP BY COLOR SHOP BY COLOR

• 2400K
• 2700K
• 3000K
• 3200K
• 4000K
• 5000K
• 5600K
• 6500K
• SimpleColor LED Strips

RESOURCES RESOURCES

• SPD SIMULATOR
• CUSTOM SPECTRUM
• LEARN LED STRIPS
• CCT SIMULATOR
• HIGH CRI
• BLOG

REACH OUT REACH OUT

• REVIEWS
• ABOUT US
• GET SUPPORT
• ACCOUNT

E26 vs E27 Bulbs - Interchangeable? Not Necessarily! Home / Blog / Home & Residential / E26 vs E27 Bulbs - Interchangeable? Not Necessarily! You may be wondering if E26 and E27 are the same or interchangeable, and if you can use an E26 bulb in an E27 socket, or vice versa. Before you proceed, you should know that there are safety risks involved! A Convergence of Two Voltage Standards Prior to the development of new, energy-saving bulbs such as CFL and LED bulbs, incandescent bulbs operated on a particular voltage level only - 120V AC for North America, and 240V AC for Europe (and other 240V AC countries). There was no such thing as a "wide voltage" incandescent bulb that worked both with 120V AC and 240 V AC. The 120V AC versions used E26 lamp bases, while the 240V AC versions used E27 lamp bases - similar but slightly different screws. Because the voltage ratings differed, there was almost never a case where the incandescent E26 lamps would or could be used in an E27 socket at 240V AC, and vice versa, since there would be an inherent voltage incompatibility. With the development of CFL and LED bulbs, however, lamps became compatible with a wide range of voltages. Specifically, some LED lamps can operate at any voltage level between 90V AC and 240V AC. The same LED lamp can therefore be used on a 120V AC circuit in North America, as well as a 240V AC circuit in Europe. But then, the question arises, should the LED lamp use the E26 or E27 Edison Screw standard? And, furthermore, if an E26 LED bulb is rated for use at 240V AC, can it be used in an E27 socket, and vice versa? Beware of Incorrect Advice! Many manufacturers and light bulb sellers will simply state that E26 and E27 bulbs and sockets are interchangeable. They will claim you can safely install an E26 bulb in an E27 socket, and vice versa. Furthermore, the common reasoning they give is that "well, E27 is 27 mm and E26 is 26 mm, and we know they fit, so close enough!" This is inaccurate advice based on incorrect information! When manufactured to the universally accepted IEC standards, E26 and E27 lamp bases actually have the same diameter specifications of 26.05 mm (min) to 26.45 mm (max). What is different between E26 and E27 are the minimum distances between the bottom contact (live contact) and the screw threads. The motivation for this difference is due to the different line voltage levels the E26 and E27 standards are designed to - 120V AC and 240V AC, respectively. You will indeed almost always find that E26 and E27 lamp bases are mechanically interchangeable - i.e. you will be able to physically fit an E26 bulb into an E27 socket, and vice versa. However, just because a bulb fits and operates, does not necessarily mean that your lamp installation meets the electrical safety standards that the lamp and lampholders were designed for. In fact, a mismatched installation can lead to an increased risk for short circuits and electrical fires. In general, bulbs with an E27 designation are safe to use in E26 lampholders, but E26 bulbs may pose an electrical safety hazard when used in E27 lampholders and 240V AC. This is because E26 bulb bases are assumed to only receive voltages up to 120V AC, and not 240V AC. Higher voltages require a wider separation of live and neutral contacts, and therefore E27 has stricter requirements on the separation distance. Below, we go in depth into the difference between E26 and E27. Mechanical differences between E26 and E27 Manufacturing of Edison Screw lamp bases are governed by the IEC standards, which lay out the required dimensions under IEC 7004-21A-2, and IEC 7004-21-9, for E26 and E27, respectively. Despite what is commonly described as a 1 mm difference between E26 and E27 screw dimensions, the screw dimensions requirements are virtually the same. The most significant differences are seen in: 1) Overall screw length, 2) Screw thread diameter at trough, and 3) Insulator cap height. Below are diagrams and specifications comparing E26 to E27: Length of screw (min): E26 - 19.56 mm E27 - 22.0 mm Screw diameter at thread peak: E26: 26.05 mm - 26.41 mm E27: 26.05 mm - 26.45 mm Screw diameter at thread trough (max): E26: 24.72 mm E27: 24.26 mm Distance between threads (OC): E26: 3.629 mm E27: 3.629 mm Live contact pad width: E26: 9.14 mm - 11.56 mm E27: 4.8 mm - 11.5 mm Insulator height (min): E26: 3.25 mm E27: 5 mm Electrical Safety Differences Between E26 and E27 The mechanical differences we discussed above may seem inconsequential, but exist due to the corresponding voltage level that each lamp base is designed for. E26 lamps are designed for the North American market, which primarily uses 120V AC, while E27 lamps are designed for other markets where 240V AC is the norm. Because E27 bulbs are designed for use with higher voltage circuits, additional precautions must be taken to ensure that there is sufficient clearance between the live and neutral contacts. Specifically, the mechanical differences we note above exist because: 1) E27 uses a longer length screw, because the longer length provides additional alignment precision of the screw in the socket. If the screw is improperly aligned, the "live" contact point may come closer to the neutral screw threads, increasing the risk of an electric arc or short circuit. 2) E27 uses a wider thread trough diameter, to provide a more secure and tight contact. This provides additional protection against moisture and debris from entering the socket. At higher voltage levels, the short circuiting and electrical fires risks are elevated by moisture and contamination. 3) E27 requires a taller insulator height to increase the distance between the live contact and the neutral screw base. The difference is relatively significant and necessary to avoid short circuit risks. Bottom line When purchasing LED bulbs, do not blindly assume that E26 and E27 are fully interchangeable. When possible, use E26 bulbs for E26 sockets at 120V AC, and E27 bulbs for E27 sockets at 240V AC. In some cases, E27 bulbs may be safely used in E26 sockets, but E26 bulbs should not be used in E27 sockets. Even though they may be mechanically similar and interchangeable, from an electrical safety standpoint, E26 offers lessened insulation and protection against short circuits and electrical fires when used in an E27 socket at 240V AC.

Other Posts

Top 4 Things to Consider When Buying LED Spotlights

In recent years, you may have found that the halogen bulb you've been buying for years is no longer available at your local hardware store. ...Read More

Troubleshooting LED Strip Problems

LED strips come in a very wide variety of sizes, ...Read More

Electrical Principles Behind LED Strip Length Limitations

LED strip lights are extremely popular due to their versatility. The ability to cut LED strip lights to any desired length is certainly a hu...Read More

Aluminum Channels for LED Strip Lights - Are They Worth It? An In Depth Look

One of the most popular accessories for our LED strip lights include our ...Read More

Back to Waveform Lighting Blog

Browse our collection of articles, how-to's and guides on various lighting applications as well as in-depth color science articles.

Browse Waveform Lighting Products

A-Series LED Bulbs

Our A19 and A21 lamps fit in standard lamp fixtures and are perfect for floor and desk lamp fixtures.

Candelabra LED Bulbs

Our candelabra LED bulbs offer soft and warm light output in a decorative bulb style that fits E12 lamp fixtures.

BR30 LED Lamps

BR30 lamps are ceiling lamps that fit in residential and commercial fixtures with 4-inch or wider openings.

T8 LED Lamps

Directly replace 4-ft fluorescent lamps with our T8 LED tube lights, compatible both with and without ballasts.

LED-Ready T8 Fixtures

LED tube light fixtures pre-wired and compatible with our T8 LED lamps.

LED Linear Fixtures

Linear lamp fixtures in 2-ft and 4-ft lengths. Plugs into standard wall outlets nd mounts using screws or magnets.

LED Shop Lights

Overhead light fixtures with hanging chains. Plugs into standard wall outlets.

UV-A LED Lights

We offer 365 nm and 395 nm LED lights for fluorescence and curing applications.

UV-C LED Lights

We offer 270 nm UV-C LED lights for germicidal applications.

LED Modules & Accessories

LED PCBs, panels and other form factors for a variety of industrial and scientific applications.

LED Strip Lights

Bright LED emitters mounted on a flexible circuitboard. Can be cut-to-length and installed in a variety of locations.

LED Strip Dimmers

Dimmers and controllers to adjust LED strip lighting system brightness and color.

LED Strip Power Supplies

Power supply units to convert line voltage to low voltage DC needed for LED strip light systems.

Aluminum Channels

Extruded aluminum channel profiles for mounting LED strip lights.

LED Strip Connectors

Solderless connectors, wires and adapters to join and connect LED strip light system components together.

COMPANY INFO

About Us Blog Support Center Frequently Asked Questions Careers Waveform Lighting Japan

HELP & SUPPORT

Learning Center Knowledge Base Product Reviews Get Support

REPLACEMENT LAMPS & BULBS

A-Series LED Bulbs Candelabra LED Bulbs BR30 LED Lamps T8 LED Lamps

LED LIGHT FIXTURES

LED Linear Fixtures LED Shop Lights LED-Ready T8 Fixtures

ULTRAVIOLET

UV-A LED Lights UV-C LED Lights

LED STRIP LIGHTS & COMPONENTS

LED Strip Lights LED Strip Dimmers & Power LED Strip Accessories LED Modules & Components

LIGHTING APPLICATIONS

Horticulture Film & Photo D65 Bias Lighting Jewelry & Display Human Centric Color Matching Art & Painting Aquarium Home & Residential Avian Full Spectrum realUV™ cleanUV™ Vanity PCB Designs

OUR TECHNOLOGIES

Learn About LED Strips Learn About LED Tube Lights SimpleColor™ LED Strips Flicker-Free LED ModernVintage™ Incandescent Bulb Replacements High CRI LED Lighting High CRI LED Strips Full Spectrum ABSOLUTE SERIES™ 99 CRI

TOOLS & CALCULATORS

Lumen Estimation Calculator LED Strip LayoutMaps™ Spectrum Simulator Custom LED Spectrum CRI Calculator CCT Simulator © 2025 Waveform Lighting, LLC. All rights reserved. 4400 NE 77th Ave Ste 275, Vancouver, WA 98662, USA Privacy Policy | Terms of Use