If the fluorescent light in your home has gone dim, started flickering, or stopped working completely, the first question is always the same: “Which fluorescent tube do I need?”
This guide will help you identify the correct T8 fluorescent tube, G13 lamp, or 2D lamp replacement quickly, using simple checks that anyone can follow.

At OldLightFittings.com, we specialise in hard-to-find fluorescent tubes and older lighting replacements, so this guide is designed to save you time and prevent buying the wrong lamp.

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⭐ 1. Identify Your Fluorescent Tube Type (T8, G13)

The vast majority of older UK homes use T8 fluorescent tubes. These are the standard tubes with a G13 cap — two metal pins on each end.

T8 Tube Sizes (Most Common):

• 2ft – 15W

• 3ft – 18W

• 3ft 6" – 30W

• 4ft – 36W

If your tube matches one of these lengths and wattages, you need a T8 G13 fluorescent tube replacement.

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⭐ 2. Match the Wattage — This Is the MOST Important Step

Fluorescent tubes must be replaced with the same wattage as the original tube.

For example:

• Your tube says 18W → buy a T8 18W replacement

• Your tube says 36W → buy a T8 36W replacement

Using the wrong wattage can cause:

• flickering,

• dim light,

• or the tube not lighting at all.

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⭐ 3. Choose the Right Colour Temperature (3000K, 3500K, 4000K, 6400K)

Fluorescent tubes come in four main colour temperatures:

3000K – Warm White

Soft and cosy. Ideal for living rooms and hallways.

3500K – Neutral White

Balanced, natural light for general use.

4000K – Cool White

Bright white light — perfect for kitchens, garages, workshops.

6400K – Daylight White

Very bright, clear light for visibility and detailed work.

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⭐ 4. Check the Tube Length (2ft, 3ft, 3.5ft, 4ft)

If you don’t know the wattage, you can measure the tube:

• 2ft = 15W

• 3ft = 18W

• 3ft 6" = 30W

• 4ft = 36W

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⭐ 5. When You Need a 2D Lamp Instead

If your fitting is a bulkhead (flat, round or square ceiling light), you most likely need a 2D lamp rather than a tube.

Most common UK sizes:

• 16W 2D Lamp

• 28W 2D Lamp

• 38W 2D Lamp

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⭐ 6. Problems That Are NOT the Tube (Starters & Ballasts)

If your tube is flickering, buzzing, or slow to start, the issue may be:

✔ The starter

Cheap and easy to replace.
Fixes: flickering, slow start, dull light.

✔ The ballast

Controls the tube’s power.
If a tube refuses to light even when new, the ballast may be failing.

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⭐ 7. Why Buy Fluorescent Tubes Online Instead of In-Store?

Many local shops and DIY stores no longer stock older fluorescent sizes.
At OldLightFittings.com, we specialise in:

• T8 fluorescent tubes (15W, 18W, 30W, 36W)

• G13 replacement lamps

• 2D lamps (16W / 28W / 38W)

• Starters (FSU, FS125, etc.)

• Hard-to-find lighting for older fittings.

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⭐ Final Tip: Send a Photo if You’re Unsure

If you’re not certain which lamp you need, just send us a picture of your old tube or fitting.
We identify the correct tube 100% of the time.