Crack Your Light Bulb Codes - Get The Right Type & Size LED

Working out how 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 light bulb has a unique code associated with it. It's clearly printed on the base of the bulb 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, 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.

What the Letters Mean

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

E Edison Screw Base
The Edison screw base was developed by Thomas Edison himself.
The bulb has a threaded metal base which screws into a matching socket.
This 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.  

It 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.

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 haogens.

G Glass Type Lamp  This is a historical term that's still hanging around.
U U-Shaped 'U' shaped ceramic base mount found on GU10 lamps.
T Tube

e.g. Tubular fluorescent

What the Numbers Mean

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.

Our LED replacements for common lighting types.

These are some of our LED replacements for common lighting types.

Putting It All Together

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 style light bulb (Bayonet mount with 22 mm diameter)
  • E14 - candle style light bulb (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 product code down, the only thing left is choosing your colour temperature and beam angle. Oh wait, don't forget about energy efficiency and cost! Here's another blog post entitled "8 things to check when buying your next light bulb" that might shed some more light on the issue...

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

By Juliet Guterres | | LED, Lighting |
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Reduction Revolution Pty Ltd (ABN 74 141 672 764) is an Australian-owned company focused on energy efficiency and sustainability.

Since 2010 we have supplied thousands of customers with training, advice, monitoring, lighting, and innovative energy saving products.

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