When you shop for bulbs online and you’re comparing a product image on the computer screen to the old bulb you have in your hand, it’s hard to tell if the screw or bayonet cap is the right size. This is made even worse with small screw caps where there are only a few millimetres difference between the sizes.

But don’t worry, once you know what the cap types mean, and with the aid of your trusty tape measure or ruler, you can be confident you’ll order the right bulb every time.

Browsing the online shop you’ll need to look in the product’s description or specification for the code used to describe the cap of the bulb. For screw in fittings it will start with a letter ‘E’ which stands for Edison Screw. The second part will be a number which corresponds to the diameter of the lamp holder the bulb’s screw goes into, so an E10 screw fits in a 10mm diameter holder, an E14 screw fits into a 14mm diameter holder and so on…

Notice I said it’s the diameter of the lamp holder and not the bulb’s screw? That’s because the actual screw cap on the bulb is slightly smaller in diameter than the fitting. If they were both exactly the same size then the screw wouldn’t fit! The exact measurements of the screw caps are:

All of our product pages show the cap fitting in the product specification.

E10

Can also be referred to as MES, Miniature Edison Screw. These are commonly found in old chandeliers and so the bulbs designed to fit e10 lamp holders tend to more decorative in appearance to suit the light fitting. You will also find bulbs with E10 caps in miniature lamp applications and indicating panels.

E10 candle bulbs >  |  E10 Panel bulbs >

E12

Is a size more commonly found in America and is used in old or imported candelabra fittings. It is the least common of the screw sizes so is unlikely to be stocked in your local supermarket. Luckily you can still find a good range online from specialist bulb suppliers (just like us!).

E12 candle bulbs >

E14

Or SES standing for Small Edison Screw is a very common size used throughout Europe and the UK. It is found in many types of small light fittings around the home from bedside table lamps to wall lights and chandeliers. Many shapes of bulb are available with an E14 cap including Candles, Golf balls, small reflector spot lights and small decorative filament bulbs. Be sure to know what shape will best suit your fitting.

E14 candle bulbs >  |  E14 golf ball bulbs >

E27

Known as ES for Edison Screw. This is the standard screw size used in most large mains voltage light fittings. It’s uncommon for this size to be used in a delicate chandelier or an old fitting but there are always exceptions. Again a wide range of shapes will be available for bulbs with an E27 cap. 

E27 Candle bulbs >   E27 golf ball bulbs >   E27 GLS bulbs >   E27 globe bulbs >