The difference is 13 millimetres and it is all in the base. E14 has a 14mm screw thread, E27 has a 27mm one. The 'E' stands for Edison screw and the number is simply the width of that screw in millimetres. E14 is the small one used in chandeliers and lamps, E27 is the standard one used in ceiling fittings and most household bulbs. They both twist in, and they do not swap without an adapter.
It sounds like the sort of thing you should already know, and then you are standing in the kitchen at eight on a Sunday holding a dead bulb, squinting at a code printed in grey on grey, wondering why the spare in the drawer refuses to go in. This is the single most common bulb question we get, and it has one of the tidiest answers in all of lighting. Learn the two numbers once and you never guess again.
The short answer: it is the width of the screw
Both E14 and E27 are Edison screw fittings, named after the man who threaded a light bulb in the first place. The letter never changes. Only the number does, and the number is the diameter of the metal base in millimetres.
- E14 is 14mm across. In the UK you will also see it written as SES, for Small Edison Screw.
- E27 is 27mm across. You will also see it as ES, for Edison Screw, sometimes called the standard or medium screw.
That is the whole distinction. Everything else, the shape of the glass, the brightness, the room it belongs in, follows from that one measurement. If you remember nothing else, remember that the bigger number is the bigger bulb.
Is E14 or E27 bigger?
E27 is nearly twice the width of E14, so the E27 is the larger of the two by a comfortable margin. Hold them side by side and there is no mistaking them. The E27 base is chunky, the sort of thing you screw into a table lamp without thinking. The E14 is slim and neat, the size that suits a candle bulb on a chandelier arm.
Because it is larger, the E27 comfortably carries higher-output bulbs and does the heavy lifting of general room lighting. The E14, being smaller, tends to live in fittings where the bulb is meant to be seen and stay discreet. Size is not about quality here. It is about where the fitting sits and how much room the maker left for the base.
Where each fitting is used
Once you know which is which, you start spotting them everywhere. There is a rough logic to where each one turns up.
| E14 (SES, small) | E27 (ES, standard) | |
|---|---|---|
| Base diameter | 14mm | 27mm |
| Also known as | SES, Small Edison Screw | ES, Edison Screw, standard or medium screw |
| Fitting method | Screw (twist in) | Screw (twist in) |
| Common bulb shapes | Candle, golf ball, small globe, pygmy | Classic pear (A60), globe, reflector, spiral |
| Typically found in | Chandeliers, wall lights, bedside and desk lamps, cooker hoods, some fridges and ovens | Ceiling pendants, table and floor lamps, main room lights, outdoor lanterns |
| Job in the room | Decorative and accent, usually several small bulbs | General and task, usually one brighter bulb |
The pattern, if you want a rule of thumb: E14 is the fitting for lights you look at, E27 is the fitting for lights you see by. A five-arm chandelier almost certainly takes E14 candles. The pendant over your dining table almost certainly takes a single E27. It is not a law, and plenty of fittings break it, but it will steer you right nine times out of ten.
How to tell which fitting you have
You do not need to guess and you certainly do not need to buy one of each and see which fits. There are three reliable ways, in order of how little effort they take.
- Read the label. Look on the old bulb's base or on the fitting near the socket. You are looking for E27 or ES, E14 or SES. Most fixtures also print a max wattage next to it, for example 'Max 40W E14', which tells you the cap and the ceiling in one line.
- Measure the base. If nothing is printed, take a ruler to the widest part of the metal screw. Roughly 14mm means E14, roughly 27mm means E27. There is no size in between the two, so you will not be caught in a grey area.
- Photograph it before you leave the house. The oldest mistake in the book is trusting your memory to the shop. Take the dead bulb with you, or at the very least a clear photo of the base. It costs nothing and saves the second trip.
Our honest advice, and we will die on this hill: take the actual bulb. A grainy phone photo of a base in a dim hallway has sent more people home with the wrong bulb than any other single thing. The bulb in your hand cannot be misremembered.
Can you swap an E14 for an E27, or the other way round?
Not directly. An E27 bulb is far too wide to thread into an E14 socket, and an E14 bulb will just rattle around loose in an E27 without ever gripping. The sizes are fixed and they do not meet in the middle.
Screw adapters do exist. A small collar screws into one size and gives you the other, so you can put an E27 bulb into an E14 fitting or the reverse. They are cheap and they work. We are not going to pretend they do not.
What we will say is that an adapter is a fix, not a plan. It adds length, so the bulb can end up poking rudely out of a shade that was never sized for it, and on a small E14 fitting you must keep the bulb's wattage inside what that little holder was built to take (and if you plan to dim them, check the bulb says dimmable). If you are choosing bulbs for a fitting you own, buy the right cap from the start and skip the adapter entirely. If a chandelier was designed for E14 candles, that is what belongs in it. The maker did not fit a small holder by accident.
Which is brighter, E14 or E27?
Neither, and this is the myth worth killing. The cap size has nothing to do with brightness. Brightness is measured in lumens, and lumens are set by the bulb you buy, not by the width of its screw. You can find a dim E27 and a bright E14 without much looking.
What is true is that the larger E27 body has more room for higher-output bulbs, so at the very top end you will find brighter bulbs in E27 than in E14. But for the everyday range, both give you plenty of choice. If someone tells you to fit E27 because it is 'brighter', they are half right by accident and fully wrong in principle. Choose the fitting your light takes, then choose the lumens you want. Do not choose a bulb by the size of its cap and hope.
The everyday confusion: screw versus bayonet
Here is the trap that catches more UK households than the E14 versus E27 question ever does. Not every bulb screws in. Plenty of older British homes run on bayonet fittings, where the bulb pushes in and twists a quarter turn to lock, with two little pins on the sides of the base instead of a thread.
- Screw caps start with 'E', for Edison. E14 and E27 are both screw.
- Bayonet caps start with 'B'. B22 (also BC, Bayonet Cap, 22mm) is the big one, B15 (SBC, small bayonet) is its little sibling.
So the real first question is not 'which screw size', it is 'screw or bayonet at all'. Look at the base. Threads mean screw, two side pins mean bayonet. Get that wrong and no amount of measuring the diameter will help you, because you are comparing a bulb that twists in against a socket that wants a push and a click. Sort that first, then sort the number.
The short version
- E14 and E27 are both Edison screw fittings. The number is the base width in millimetres.
- E14 is 14mm (SES, small), for chandeliers, wall lights and lamps. E27 is 27mm (ES, standard), for ceiling fittings and most household bulbs.
- E27 is the bigger of the two, by nearly double.
- They do not swap without an adapter, and an adapter is a fix, not a plan.
- Cap size does not set brightness. Lumens do.
- Check whether your fitting is screw (E) or bayonet (B) before anything else.
Once you know your fitting, the bulb is the easy part. The fixture is where the choosing actually matters. If you are shopping for the light itself, most decorative and chandelier styles in the KES wall lights range take E14, while pendants and larger pieces in the ceiling lights collection usually take E27. The product page will always list the cap, so you will know exactly what to buy before it arrives.
Frequently asked questions
Is E14 or E27 bigger?
E27 is bigger. Its screw base is 27mm across against the E14's 14mm, so it is nearly twice the width. The bigger number is always the bigger bulb.
Can I use an E27 bulb in an E14 socket?
Not directly, an E27 is far too wide to thread into a 14mm E14 socket. A screw adapter can bridge the two, but check the fitting's max wattage and make sure the longer bulb still fits your shade.
What does the E stand for in E14 and E27?
Edison screw, after Thomas Edison, who designed the threaded base. The number after it is simply the diameter of that screw in millimetres.
Are E14 and E27 the same as SES and ES?
Yes. E14 is the same as SES, Small Edison Screw. E27 is the same as ES, standard or medium Edison Screw. They are just the letter code and the trade name for the same fitting.
Which gives more light, E14 or E27?
Cap size does not decide brightness, lumens do. The larger E27 body does allow higher-output bulbs at the top end, but both fittings offer plenty of choice for everyday lighting.
Words by Reece Knight, KES Lighting & Home. Last updated 7 September 2026.
