Working out how the various types of light bulbs are named and categorised can be a bit tricky at first. But after reading this handy guide, you'll soon be decrypting labels like Tom Hanks in the DaVinci Code.

Every type of light bulb has a unique code associated with it. It's clearly printed on the base of the globe and on the packaging.

These codes are usually a combination of letters and numbers. Over time, the more historically popular lighting types have become standard, and these are the ones that we've tried to cover here.

Once you get a hang of these codes, you'll no longer feel the need to bring the old globe into the shop to check it with the new one, and shopping online will be a breeze.

Light Bulb Types - What the Letters Mean

The letters usually refer to the fitting type or another feature of the light globe. For example:

Letter Meaning Light Bulb Type Notes
E Edison Screw Base The Edison screw base was developed by Thomas Edison himself. This light bulb type has a threaded metal base which screws into a matching socket. These became the standard in Northern America and continental Europe for general purpose lighting. For example, you might have noticed that Ikea uses a lot of E14 'small edison screw' bulbs in their lamps and lighting fixtures.
B Bayonet Cap Base The Bayonet cap has radial pins on the base of the light bulb that slip into L-shaped holes in the socket. This type of light globe is traditionally the standard in Britain and colonial countries. Historically, it is similar to the fastening used for quickly attaching bayonets to rifles, hence the name.
R Reflector Style Lamp Reflectors are domes covered in reflective material that surround the light source in order to gather and reflect the light back into a more concentrated beam of light. They often have a faceted surface, such as the “multi-faceted“ reflector used in MR16 halogens.
G Glass Type Lamp  This is a historical term that's still hanging around for certain light bulb types (even if they are no longer made from glass).
U U-Shaped 'U' shaped ceramic base mount found on GU10 lamps.
T Tube e.g. Tubular fluorescent

What the Numbers Mean - Type & Size of Light Globes

The numbers generally refer to the distance between the electrical connectors or the width of the lamp.

Depending on the origins of the lamp, this measurement can either be in inches or millimetres.

Types of LED Lights

These are some of our LED replacements for common light bulb types.

Putting It All Together - Light Bulb Types

Put the letters and numbers together and things start to make a little more sense, now that you know what to look for. Listed below are a range of the most commonly used lamps that we now sell low energy LED replacements for:

  • MR16 - 'low voltage' down-lights (Multifaceted Reflector with 16 eighths of an inch front diameter)
  • GU10 - 'mains voltage' down-lights (originally Glass style with 10 mm between the pins)
  • B22 - regular light bulb type (Bayonet mount with 22 mm diameter)
  • E14 - candle light bulb type (Edison screw with 14 mm thread diameter)
  • T8 - office lighting tubes (Tubular fluorescent of 8 eighths of an inch diameter)
  • AR111 - retail store lighting (Aluminium Reflector with a 111mm front diameter) 

Now you've got the light bulb type / code down, the only thing left is choosing your colour temperature and beam angle. Oh wait, don't forget about energy efficiency and cost!

See our full range of quality LED bulbs and light fittings.

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