We are talking about lamp caps. ‘Lamp caps’ are the part of a light bulb which makes the electrical connection with your light fitting.
These can often be described as BC (bayonet) or ES (Edison Screw developed by Thomas Edison), but in the case of screw-in bulbs there are quite a few similar names or codes for bulbs which are very similar – but get the wrong lamp cap and the bulb simply won’t fit!
So what is the difference and what do all the codes and numbers mean?
A ‘standard’ ES (Edison screw) bulb is also known as E27, which you might see on some light bulb boxes. This is the diameter of the screw thread, i.e. 27mm in diameter.
The only larger screw fitting that you are likely to see is in some high-bay fittings (e.g. a barn or warehouse). They use E40/GES (Giant Edison Screw) bulbs, which are 40mm in diameter, but they aren’t normally used in the home.
The other most common screw-in bulb for the home is the E14 or SES (Small Edison Screw). This, as you will have correctly guessed has a 14mm diameter screw cap.
I don’t have a ruler handy…
Ok, the easiest way to tell an E14/SES bulb from an E27/ES bulb is:
- E27/ES: roughly the same width as your thumb – find E27/ES replacement bulbs
- E14/SES: roughly the same width as your little finger – find E14/SES replacement bulbs
Other screw-cap bulbs
Other screw capped bulbs that you might be looking for, especially if you need a replacement pygmy bulb are:
- E17/IES (17mm diameter) Intermediate Edison Screw, sometimes used in microwaves – find E17 replacement bulbs
- E12/CES (12mm diameter) Candelabra Edison Screw, sometimes used in boats and some Christmas decorations – find E12 replacement bulbs
- E10/MES (10mm diameter) Miniature Edison Screw, used in torch bulbs and other very small applications – find E10 replacement bulbs
Table of Edison Screw-cap fittings
| Designation | Base Diameter (Crest of thread) |
Name | Usage |
|---|---|---|---|
| E5 | 5 mm | Lilliput Edison Screw (LES) | Very uncommon |
| E10 | 10 mm | Miniature Edison Screw (MES) | e.g. torch bulbs |
| E11 | 11 mm | Mini-Candelabra Edison Screw (mini-can) | Very uncommon |
| E12 | 12 mm | Candelabra Edison Screw (CES) | Candelabras, boats and some Christmas decorations |
| E14 | 14 mm | Small Edison Screw (SES) | Common household bulb, pygmy version used in inflatable Santas |
| E17 | 17 mm | Intermediate Edison Screw (IES) | e.g. microwaves |
| E26 | 26 mm | [Medium] (one-inch) Edison Screw (ES or MES) | Very uncommon |
| E27 | 27 mm | [Medium] Edison Screw (ES) | Common household screw-in bulb |
| E29 | 29 mm | [Admedium] Edison Screw (ES) | Very uncommon |
| E39 | 39 mm | Single-contact (Mogul) Giant Edison Screw (GES) | Very uncommon |
| E40 | 40 mm | (Mogul) Giant Edison Screw (GES) | High-bay barns and warehouses |
We recommend measuring the screw thread of the bulb (preferably with calipers) to work out which type of bulb you need.
For much more information about Edison screw bulbs, try this Wikipedia article: http://en.wikipedia.org/wiki/Edison_screw
I just wanted to let you know that I found this page extremely helpful and it answered my query regarding E14 and SES bulbs within seconds!! (I didn’t know if they were the same bulb or not)- Thanks!! 🙂
Found this page thanks to Google, E12 candelabra ES used in some 240v night lights and would you Believe we used to use hundreds of 24v LES lamps in railway signalling panel indications, surprisingly we started replacing these with LED’s over 15 years ago!
Hi Martin
Thank you for the message. We do have some E12 bulbs but if you need something that you can’t find on our site, please get in touch as we can often source it!
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How many times have you bought ES bulbs an found you have bought the wrong sizes.
this chart should stop you suffering this in future, very helpful!!
Glad you found it useful! Let us know if we can help with your bulb choices too.
Hi I wonder if you can help
I have bought a ES e27 candle bulb to replace a round ES e27 bulb but the solder on the end is flat meaning it will not light. I assume it is because the solder is not touching the lamp contact but wanted to knbnow if you have come across this problem before and is it just a fault with the brand I have bought
many thanks
Pedro
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I have a bulb, screw base, that measures 11.62mm at the crest of the threads, it is an elongated bulb, kind of an oval shape with a slightly pointed tip. Similar shape to a classic Christmas light, but much smaller base.
Is this e11, or e12? Written on the base of the bulb is syl60w120v Korea syl60w120v
It came out of a ceiling mounted light in my house, that was installed sometime before I moved in, and after the house was built, 100 years ago. There are 4 of them, and no stickers or writing on the light it’s self.
Please help ASAP, I need to order replacement bulbs
Thank you so much for your information. Was standing in the supermarket for 10 mins trying to find what I needed totally confused by the labelling and then a brainwave to do a Google search led me to you. Very useful page thank you!
I am screwed. (Pun intended.)
I am measuring 15 mm. So, it could be e 17 or e 14. Which?
Very helpful comparison of bulb cap sizes; a really useful education for me -thank you!
Very helpful information about various bulb cap sizes etc. Thank you!
Hi, this site is helpful from a European point of view, but as an American I was misled until realizing the “.co.uk” part of the URL. It would be nice to mention regions in the list of screw types. For example, you say that E26 is “Very uncommon” but that’s what we use on this side of the ocean. You could say “Very uncommon in Europe, used in the New World” and vice versa for E27. Also, E12 is our common small base (similar to your E14). Thanks! :o)
This sounds like an E12 bulb. Light bubs with an E12 screw cap are also sometimes ‘candelabra bulbs’, which would make sense based on your description.
The light bulb challenge completely demystified for me. How come nobody ever explained this to me so clear? So simple is embarrassing! Thank you so much.
Thank you – very useful!