T5, T8 or T12? Which Tube Do I Need And Why?

Terms like T5, T8 and T12 may seem like meaningless jargon to the layman and it might be hard to figure out which type of tube is best for your needs. The truth is these terms are pretty easy to get your head round and the differences between these types of fluorescent tubes are simple and easy to understand.

What do the acronyms stand for?

T simply means tubular and the numbers indicates the diameter of the tube. The T__ acronym is a standard for expressing the measurement of the diameter of the tube in 1/8ths of an inch. So a T5 is 5/8ths of an inch, a T8 is exactly one inch thick (i.e. 8/8ths) and a T12 is 12/8ths or one and a half inches thick.


A t5 fluorescent tube is generally considered to be the most energy efficient fluorescent tube. Set to last for on average 30,000 hours it falls into the A class energy efficiency rating. There are a number of factors which set the T5 apart from other tubes. These include:

  • Colour Rendering Index: 85CRI
  • Quantity of light measured: 103LPW
  • Co-efficiency of utilization: .90CU

A T5 comes in then at 51% more efficient than a T12 and 9% more efficient than a T8.


A T8 is like a mid-range tube. It’s better for the environment than a T12 but it’s not quite as efficient as a T5. However, it’s not drastically far off a T5 and in some instances is significantly cheap to buy and fit making it appealing to some. Consumers might pick a T8 over a T5 if they want to save on costs and if they are using bulbs in extreme conditions and need something which they know to be reliable. A lot of factories and warehouses will use T8 and therefore be keen to continue using these bulbs if they think they’re a safe bet.


T12’s are particularly inefficient and since the release of T8 and T5 have now been phased out. You can still buy T12s but they’re not being manufactured, produced or imported in and into the UK. If you’ve been using T12s and you want to change, in most circumstances an equivalent length T8 will replace your T12 perfectly. Old-style T12’s were withdrawn from 1st April 2012.

If you’re looking for the most eco-friendly fluorescent tubular light then the T5 is for you. However, the T8 offers similar advantages to the T5 for a lower price so it’s certainly worth considering if you’re on a budget.

Please note: the information in this article is provided as a guide only. We strongly recommend speaking to an electrician before attempting any electrical work yourself. Any links included in this article are for information purposes only and Lamp Shop Online does not endorse the websites linked to.

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Published 2015/09/08

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