Fluorescent Tube Sizes - A Guide to T4, T5, T8 & T12 Tubes | LED Light Guides (2023)

Fluorescent tube lighting comes in a range of sizes. When you are trying to replace fluorescent lighting, whether, with LEDs or another tube, you will need to understand the difference between tube light sizes.

Determining the tube size of the fluorescent light will help you decide which tube lighting is a suitable replacement. The tube size will also be a clue on the best method for converting fluorescent tubes to LED.

Even if you are not planning on converting fluorescent lights into LED tube lights, knowing about the differences between the sizes is still imperative. Each fluorescent lamp has its own advantages and disadvantages not only because of size but the lumen output (brightness).

Table of Contents

Fluorescent Tube Sizes Guide

There are 4 different fluorescent light options; T4, T5, T8, and T12.

The T stands for tubular and the numbers are an index for the diameter (in inches) of the tube. Most tube lighting will have its size mentioned on an end of the tube. So, in most cases, you won’t have to physically measure the tube’s diameter and length.

If the size tag is missing, use the overview below for quick reference.

Tube Light TypeSize IndexDiameter in InchesDiameter in Millimeters

Aside from the size, you need to check the lighting fixture requirements for being compatible with the bi-pin base type and the milliamps.

But first, you must know whether you are looking for office lighting with a lot of lumens or something with a softer light as this will make a difference to the option you require.

T4 Fluorescent Lights

Fluorescent Tube Sizes - A Guide to T4, T5, T8 & T12 Tubes | LED Light Guides (1)

T4 tubes are the smallest of the fluorescent bulb sizes, at only 4 eighths of an inch (0.5 in). Their size is what makes T4 lights popular for under cabinet lighting purposes and accent lighting for displays or a staircase.

There is no industry standard for the length or wattage of T4 tube lights. They can range anywhere from 6 watts to 30 watts, the lower the number the lower the energy consumption, and many lengths.

If you are replacing a T4, you may struggle with finding the same fluorescent light bulbs sizes. Be sure to measure the length of the tube and check the wattage before heading for the shops or placing an online order.

T5 Fluorescent Lighting

Fluorescent Tube Sizes - A Guide to T4, T5, T8 & T12 Tubes | LED Light Guides (2)

There is not much difference in size between T5s and T4 lights. This is why the T5 is used in many of the same applications.

On the other hand, T5 tube lights are little powerhouses when comparing T5 vs T8 tube sizes. Compared to a T8, T5 tube can achieve higher luminous flux using less power.

The energy efficiency of the T5 tubes means they also last the longest, around 20,000 hours. However, this is still less than half of the expected lifespan of a T5 LED tube light which lasts an average of 50,000 hours.

If you are using T5 lights for garage lighting or an art display, then make sure that you choose a model with a higher Color Rendering Index, CRi. The CRi of T5 fluorescent bulbs generally range in the lower end of 70 -80 but there are options with more accurate color rendering up to 95. Basically that means the light color can go from daylight white to extra warm white.

Another aspect to remember about T5 fluorescent lighting is the different output possibilities. There are three levels of output available on the market; normal output (NO), high output (HO) and very high output (VHO).

The watts needed for T5 lighting will increase with the type of output. For example, a NO-T5 tube light can range between 14 watts to 35 watts while an HO-T5 fluorescent tube light will usually range between 24 watts and 80 watts.

T8 Fluorescent Lighting

Fluorescent Tube Sizes - A Guide to T4, T5, T8 & T12 Tubes | LED Light Guides (3)

The most commonly available is the T8 bulbs. This type of fluorescent tube lighting is the most popular because of its high CRi and many color temperature options.

T8 lights are a good choice for an adjustable lighting system because of their color temperature range from a soft yellow-white to bright daylight. You will also have several options that you can connect to a dimmer.

T8 lights are commonly used in larger spaces as overhead lighting for example in office spaces with troffer lights, garages or classrooms. This is why you will often see long T8 lighting in 4 foot light tubes, 6 feet, and 8 feet lengths.

Compared to T5 lighting, the 8 Foot T8 tube lights are less economical. T8 lighting tends to be more expensive and have a shorter lifespan of around 15,000 hours, but can last up to 50,000 hours if you choose the LED alternatives.

Here’s our top 3 picks for replacement 8 foot T8 light tubes:

Fluorescent Tube Sizes - A Guide to T4, T5, T8 & T12 Tubes | LED Light Guides (4)


JOMITOP 8ft T8 LED Tubes

  • Pack of 4
  • Accessories Available
  • Cool White Color
  • 35+ Reviews
Check Amazon →

Read our review

Fluorescent Tube Sizes - A Guide to T4, T5, T8 & T12 Tubes | LED Light Guides (5)


Hyperikon T8/T10/T12 8ft Tubes Lights

  • Pack of 12
  • Excellent Value
  • Bright White Color
  • 50+ Reviews
Check Amazon →

Read our review

Fluorescent Tube Sizes - A Guide to T4, T5, T8 & T12 Tubes | LED Light Guides (6)



  • Ultra Bright
  • 70+ Reviews
  • T8/T10/T12 Compatible
  • Business Friendly
Check Amazon →

Read our review

If you would like to switch out a T5 light for a T8 light or vice versa then you will need to use a ballast. Finding the correct ballast size may also take some effort as there is no industry standard for them.

T12 Tube

Fluorescent Tube Sizes - A Guide to T4, T5, T8 & T12 Tubes | LED Light Guides (7)

T12 lamps are the least popular size. This is because they use older technology that is less energy-efficient compared to the smaller options.

T12 fittings use a magnetic start ballast which is less energy efficient. The smaller and newer models have already been fitted with the more energy-efficient electric ballasts. Theballastis what regulates the current to the fluorescent lamps and provides sufficient voltage to start the lamps

However, there are still many office spaces and homes that use the T12 fluorescent tube lights, especially in older buildings. Another reason why they are still used is the cheaper purchasing price compared to the others, but, they are no longer being made.

Despite being an older model, the T12 fluorescent tube lights still offer a range of color temperatures at different watts. However, their limited lifespan of 15,000 hours still makes T12 fluorescent lights a less attractive option compared to the smaller fluorescent tube lights or LEDs.

Frequently Asked Questions:

Now you know all you need to about fluorescent tubes sizes and their differences. But below we will answer the questions that people ask us the most.

What is the difference between T5 T8 and T12 lights?

In short, the difference between t5, t8, and t12 lights are the sizes and energy efficiency. The smaller t5 and t8 tubes use less energy and have less mercury in them than T12 bulbs.

How do I know which fluorescent light bulb to buy?

When considering the question of how do I know which fluorescent light bulb to buy you need to figure out what you currently have. Once you have removed the bulb most will be marked with the type on the end, if there are no markings then you can measure the tube diameter to determine their type.

What are the different types of fluorescent tubes?

What are the different types of fluorescent tubes? There are 3 types: t12 tubes, t8, and t5 tubes, and the t12 which is the oldest and being phased out and no longer manufactured. The t8 is probably the most used with the t5 being the smallest and most energy-efficient so are often used in large office buildings and warehouses for energy savings.

How long do fluorescent tubes last?

How long do fluorescent tubes last, well that depends a lot on its wattage, design, and application, But, expect between 7,000 and 15,000 hours. But we have seen claims that the T5 can last up to 50.000 hours, but they are the newest on the block.

Think about these differences in tube lighting the next time you need to convert fluorescent lighting to LED. The different sizes are not directly interchangeable so if you want to use another size then you will have to do a bit of handiwork.

Also, don’t forget to compare fluorescent lights with the benefits of LED lighting.


What size is T5 T8 T12? ›

For example, with a T12, the diameter is 12/8, or twelve eights of an inch. Another way to say this is that the diameter is equal to 1.5 inches. For a T8, the diameter is 8/8, which is equal to 1 inch. For a T5, the diameter is 5/8, which is equal to 0.625 inches.

What is the difference between T4 and T5 fluorescent tubes? ›

The lengths of these tubes are commonly indicated by the wattage. The smallest fluorescent tube is the T2 and it has a length of between 250mm and 760mm. The next longest tube is the T4, with a total length of anywhere between 150mm and 1,500mm. This is followed by the T5, with a length of between 340mm and 1,800mm.

What size is a T4 fluorescent tube? ›

T4 fluorescent tube lights are 12mm diameter. T4 fluorescent tubes often used in kitchen under-cabinet lighting. T4 tube lights are not made in standard lengths and many manufacturers make these in unique combinations of wattages and lengths.

What is the difference between a T5 T8 and T12 fluorescent bulbs? ›

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.

How do I know what size fluorescent tube I need? ›

In order to identify which size you need, the easiest way to tell is to read the label near the base of the tube. If this information is no longer legible, you can measure the bulb's diameter. Fluorescent tubes are measured in eighths of an inch.

How do I know if my fixture is T8 or T12? ›

The main difference between T8 and T12 tubes is the tube's diameter. T12 tubes are 1.5" in diameter while T8s are just one inch. All other things—socket sizes, lengths, distance between pins—are the same. T8 LED tubes won't fall out if you try to install them in a T12 fixture—they'll fit just fine.

Are T5 tubes being phased out? ›

T5 & T8 fluorescent and compact fluorescent tubes are to be phased out. In 2023, T5 and T8 fluorescent and compact fluorescent tubes (CFL) will be phased out in accordance with the European Commission's ecodesign and RoHS directives.

Are T5 tubes banned? ›

From 1st September 2023, T5 and T8 fluorescent tubes will be phased out altogether. All business owners are required to source alternative lighting solutions and discard them as hazardous waste, or through structured recycling to be compliant.

What is the most common fluorescent tube size? ›

T8s are 1-inch diameter fluorescent tubes, and they are the most prevalent of all fluorescent tubes.

Will a T5 tube fit a T4? ›

Unfortunately, T4 and T5 fluorescent bulbs are not interchangeable due to the difference in thickness. T4 tubes are 13mm wide, and T5 tubes are 15mm wide, they also require different wattages to power and emit light.

What does the T stand for in fluorescent tubes? ›

What does “T8” mean? The “T” designation in fluorescent lamp nomenclature stands for tubular — the shape of the lamp. The number immediately follow- ing the T gives the diameter of the lamp in eighths of an inch.

What size is a T5 fluorescent tube? ›

T5 fluorescent tubes measure 16mm in diameter. They're among the more versatile of the size categories, being suitable for lighting everything from schools and office buildings to aquariums.

Can I replace T12 with T5? ›

For some applications, one T5 bulb can replace two T12 bulbs, providing even greater energy savings (a process called “de-lamping.”) The typical T12 four-lamp fixture uses 172 watts of power between the lamps and ballast. LED equivalents typically use only 50 watts, 71% less energy per fixture.

Are T12 bulbs being discontinued? ›

Why are my light bulbs phased out? In July 2012, the U.S. Department of Energy's lighting mandate took effect. Fluorescent T12 lamps and ballasts were phased out and are no longer legal to be produced or imported. This mandate was passed due to federal energy efficiency regulations.

Can you replace a T12 fluorescent with a T8 fluorescent? ›

Options for replacing T12 fluorescent tubes

The easiest and lowest price option to replace a T12 is a T8 linear fluorescent. They have become the go-to option for pre-existing T12s. If you still have magnetic ballasts, switching to a T8 will require a ballast swap.

Can I replace my fluorescent tubes with LED? ›

Yes, you can replace fluorescent tubes with LED tubes or LED-integrated fixtures. If you just want to replace the bulbs, you can use plug-and-play, direct-wire, or hybrid LED tubes. Plug-and-play tubes are the easiest to install as they do not require any rewiring to the fixture.

What happens if you use a fluorescent bulb without a ballast? ›

Since fluorescent bulbs cannot regulate current on their own, without a ballast, the bulbs can draw too much power and burn out. In addition to significantly shortening the lifespan of the bulb, this can create a safety hazard.

Can I use LED tube lights in a fluorescent fixture? ›

You have fluorescent troffers or strip fixtures already, and you're wondering if you can just pop LED tubes in them or if you'll need to change out the fixtures for something designed for LED. Good news: You can absolutely use LED tubes in your existing fixtures!

Do T8 and T12 use the same ballast? ›

Electrical compatibility is a bit trickier, because T12 fixtures will almost always contain a T12 ballast, which is not compatible with T8 lamps.

Can you replace T12 fluorescent tubes with T8 LED? ›

T8 will have one-inch diameter, the T5 will have a 5/8 diameter, and a T12 will have 12/8 inch or 1.5 inch diameter. If T8 and T12 have the same bi-pin base, then you can use the bulbs interchangeably using the same fixture just as long as you check the milliamp requirements for the ballast.

Are fluorescent lights being discontinued in USA? ›

In 2022, Vermont and California became the first states to phase out the sale of most fluorescent bulbs. Now a number of other states are considering action to phase out sales of the most common fluorescent bulbs by 2025.

Why are fluorescent lights being banned? ›

In December 2022, the Biden administration proposed regulations that would phase out compact fluorescent lightbulbs, or CFLs, as part of its larger climate change strategy. CFLs last much longer than traditional incandescent bulbs but still require more electricity than light-emitting diode bulbs, or LEDs.

Is it more economical to leave fluorescent lights on? ›

It takes more energy to start a fluorescent that it does to run it, so leave the lights on all the time to save money on your electric bill.

What is the lifespan of a T5 fluorescent tube? ›

Time: With typical daily photo periods of 8-12 hours, T5 bulbs carry the average life-span is 9-12 months. If it's been more than 12 months since your last bulb change, it's probably time for a change.

Can I replace T5 fluorescent with LED? ›

T5 LED tubes are available for plug-and-play, ballast bypass, or hybrid operation. Plug-and-play tubes operate with compatible ballasts and are installed quickly by simply removing the existing fluorescent and plugging in the LED tube.

Why are T5 bulbs so expensive? ›

T5 fluorescent bulbs are more costly than other lighting options because they require a ballast to regulate the current. However, the lower energy cost often outweighs the higher purchase price.

What is the longest lasting fluorescent tube? ›

Philips Energy Advantage T8 25W – Up to 90,000 hours.

What type of fluorescent tubes should I buy? ›

Fluorescents with a CRI of 70 and under are typically in low quality lamps. Colors in the room will appear dull and washed out. Fluorescents with a CRI of 70-79 are appropriate in commercial applications. Fluorescents with a CRI of 80-89 are appropriate in commercial and residential applications.

Are LED lights better than fluorescent? ›

Compared to fluorescent bulbs, LED lights are up to 80% more efficient. Unlike fluorescent lights, LED lights convert 95% of their energy into light and only 5% is wasted as heat; this is all while still using far less power to provide a strong and consistent output at a lower wattage.

What does T4 mean in fluorescent tube? ›

T4 (13mm Diameter)

T4 tubes have a diameter of 13mm. They're compact and easy to install making them perfect for illuminating kitchen counters and worktops as well as under cabinet lighting. These tubes will generally use between six and eight times less energy. This will save you money and help save the environment.

Do you need a ballast for a T5? ›

What type of ballast do I need for a T5 fluorescent tube? Like T8s, T5s can uses electronic ballasts of electromagnetic ballasts. You will need a ballast specific to the size of T5 tubes though.

Can I replace a T5 bulb with a T8? ›

T8 bulbs come in standard 2-, 3-, 4- and 5-foot lengths. Comparable T5 bulbs are slightly shorter than T8 bulbs. Make sure you check your existing fixture carefully because the two types of bulbs are not interchangeable.

Is T12 brighter than T8? ›

The Standard T12 lamp produces 2,650 initial lumens per lamp. The standard T8 produces 2,800 initial lumens per lamp, 6% brighter. But the standard T12 lamp produces 2,300 design lumens and the T8 produces 2,660 design lumens.

What is the difference between cool white and daylight? ›

Cool White ranges from Yellow-White (3000K) to White (4000K) to Blue-White (5000K). Daylight ranges from Blue-White (5000K) to Bright Blue (6500K). While lighting preferences are purely subjective, research has shown that these three ranges of light have different effects on sleep cycle, productivity, and mood.

Which is brighter T5 or T8? ›

Brightness. In general, the T5 light bulbs produce more concentrated lighting and higher lumen output. The T5 will give you a much brighter light than the T8 variant.

How much longer is T5 vs T8? ›

T5 LED tube is thinner than T8 LED tube, As we known, one “ T” equals the length of 1/8 inch, so ONE t8 is one inch, Simultaneously,T5 LED tube diameter is 5/8 inch.

What does T4 mean on a light bulb? ›

A: The "T" in T3 or T4 type halogen bulbs refers to the tubular shape, (not base) while the number refers to the diameter of the bulb.

What Colours are T5 fluorescent tubes? ›

T5 Coloured Fluorescent Tubes

T5 16mm diameter Coloured Fluorescent Tubes giving a high color saturation in either red, green or blue. Select either high efficiency or high output versions.

What is the lifespan of a T12? ›

The replacement LED tubes have a lifespan of 50,000+ hours and a lumen maintenance of 70%, therefore, after 50,000 hours the led tubes won't turn off; they will emit 70% of the light that they emitted originally.

Can you use a T12 ballast with T5 bulbs? ›

The good news are that now there is technology called retrofit kit that lets you transform any T8 or T12 so that it can be fitted with T5 light bulbs.

How do I know if my fluorescent bulb or ballast is bad? ›

Check the Ballast with a Multimeter

Insert one probe into the wire connector while holding the white wires together. Touch the other probe to the ends of yellow, red, and blue wires coming from the ballast. Some might exclude the yellow. If the ballast doesn't cause the needle to move, you know it needs to be replaced.

Can I replace my t12 bulbs with LED? ›

The short answer: yes. This is one of the most common questions we come across. Before you jump in and make the decision to upgrade without changing out the ballast, there are other LED solutions to consider for a high-efficiency lighting option for existing T12s.

What is the light bulb rule? ›

A federal law will take effect in 2023 prohibiting the sale of bulbs with a luminous efficacy of fewer than 45 lumens per watt. This will phase out the majority of incandescent bulbs and halogen lamps currently on the market.

How do I know if I have a magnetic or electronic ballast? ›

Simply turn the light on, then take a photo of the fixture using your smartphone or digital camera. If there are no dark bands on the resulting image, you have an electronic ballast that is likely to work with direct drop-in LED tubes (with caveats: see the next section below).

What is the difference between T5 T8 and T12 lights? ›

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.

How to convert 4ft fluorescent light to LED? ›

There are various methods for converting fluorescent lighting fixtures into LED ones. However, the simplest way is to use some sort of retrofit kit. These kits attach to already existing lighting fixtures and allow for LED bulbs to be housed in them.

What size is T8 or T5? ›

The "T" refers to "tubular," which is the shape of the bulb, while the number represents a fraction in eighths of an inch. This means a T5 bulb is tubular and is 5/8" in diameter, while a T8 bulb is also tubular and is 8/8" (meaning 1") in diameter.

What size lamp is T5 and T8? ›

Fluorescent tubes have two dimensions; diameter and length. The type of tube is determined by its diameter, with T2 (7mm), T4 (12mm), T5 (15mm), T8 (25mm), T12 (38mm) all available in multiple lengths and wattages.

What size is a T5 circular fluorescent tube? ›

The Circular Fluorescent Tube is a uniquely shaped light source that comes in T5 (15mm diameter), T6 (20mm diameter) and T9 (29mm diameter) formats.

Which is smaller T5 or T8? ›

T5 lamps are 40% smaller than T8 fixtures, but are capable of containing just as much and sometimes more light in a smaller area. In other words, more T8 fixtures are needed to produced the same amount of light generated by significantly fewer high output T5 bulbs.

What is difference between T4 and T5? ›

The T4, T4A and T5 payroll slips are a representation of your employment or commission income from a certain employer (T4, T4A) or investment income (T5). Any slip that is provided to you is also provided to the CRA.

What is the diameter of a T12 fluorescent tube? ›

A T12 lamp (on the left in the figure below) is therefore twelve-eighths of an inch, or one-and-one-half inches (3.81 cm), in diameter.

Can you replace circular fluorescent tubes with LEDS? ›

Yes, it is possible to replace a fluorescent bulb with an LED.

Which is brighter T8 or T5? ›

If you want to high bright led tube lights, you can first choose T8 led tube. because the T8 tube light is high brighter than t5 tube. T5 led tube light, which is less filled with electrons and inert gas. In contrast, If you want to creat a darker lighting environment.


Top Articles
Latest Posts
Article information

Author: Gov. Deandrea McKenzie

Last Updated: 13/09/2023

Views: 5916

Rating: 4.6 / 5 (66 voted)

Reviews: 81% of readers found this page helpful

Author information

Name: Gov. Deandrea McKenzie

Birthday: 2001-01-17

Address: Suite 769 2454 Marsha Coves, Debbieton, MS 95002

Phone: +813077629322

Job: Real-Estate Executive

Hobby: Archery, Metal detecting, Kitesurfing, Genealogy, Kitesurfing, Calligraphy, Roller skating

Introduction: My name is Gov. Deandrea McKenzie, I am a spotless, clean, glamorous, sparkling, adventurous, nice, brainy person who loves writing and wants to share my knowledge and understanding with you.