I know that standard incandescent bulbs in the US use Edison screw bases, but I'm not sure which designation / number is the one which is used for prolific non-candelabra 120 volt fixtures.

  • The US uses a 120V system, not 110.
    – Tester101
    Mar 15, 2015 at 2:14

2 Answers 2


The US 120 volt screw base is an E26. The 'E' indicates an Edison screw base and 26 is the diameter in millimeters.

Source: Wikipedia (footnote 3)

In 120-volt North America and 100-volt Japan, the standard size for general-purpose lamps is E26


For those who like to do things the hard way, it is also 7004-21A-2 (From IEC Standard sheet 60061-1 (of course)

The E26 is the 'standard' for 110 Volt systems and the E27 is the standard for 220 Volt systems. (The E27 being IEC 7004-21)

  • 2
    Really? There's only 1mm difference in diameter? That may well be the explanation for why standard light bulbs sold in the U.S, for several years now, have often had such a miserable, "tight" fit in lampholders!
    – kreemoweet
    Mar 15, 2015 at 7:43
  • 1
    In the UK, they (E27, E14) are often just called ES (Edison Screw) or SES (Small Edison Screw) - in contrast to BC (Bayonet Cap) and SBC (Small Bayonet Cap). Mar 16, 2015 at 15:20
  • 1
    @kreemoweet: I'd guess E26 is 1" and E27 is 1 1/16". "The metric system is the tool of the devil! My car gets forty rods to the hogshead and that's the way I likes it." - Thomas Edison :-). Mar 16, 2015 at 15:24
  • Furlongs per fortnight as always been my unit speed. I did learn recently about the unit of property measure, the 'chain' there being 10 square chains in an acre. (Which makes each chain a furlong, of course)
    – Some Guy
    Mar 16, 2015 at 15:40

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