The one-millimeter size difference is less important than the fixture voltage, bulb voltage, and regional safety certification.
What they share
Why these two are easy to confuse
Both are medium Edison screw-base designations, and their nominal diameters differ by only one millimeter. That visual similarity explains why a bulb may appear to thread into either socket.
Which one to use
Which specification settles the choice
Use the code and voltage specified by the fixture manufacturer. For a North American 120 V fixture marked E26, choose an E26 bulb rated for that supply. For an E27 fixture in a 220–240 V system, choose the corresponding E27 lamp and local certification.
Never assume interchangeability from physical fit alone. Read the fixture label and use a bulb approved for the local supply voltage.
Replacement check
Four details to read before ordering
- Read the base code on the old bulb and the socket or fixture label.
- Confirm the fixture supply voltage before comparing any bulb.
- Check the replacement's rated voltage range and local safety markings.
- Match shape, maximum wattage, clearance, dimming, and enclosure ratings separately.
Common questions
E26 and E27 follow-ups
Will an E27 bulb screw into an E26 socket?
It may appear to fit because the nominal diameters are close, but physical fit alone does not confirm the electrical rating or approval for the fixture and local supply.
Is E26 the same as a standard base?
In the United States and Canada, “standard” or “medium” commonly refers to E26. Read the actual E26 marking because informal names vary by market.
Does the bulb shape tell me whether the base is E26 or E27?
No. A19, A60, globe, reflector, and decorative shape codes describe the envelope. The base code and voltage must be checked independently.