LED Bulbs by Size

LED bulb sizes: choose the one that fits your fitting

The size of an LED bulb is not just a matter of looks: it decides whether the bulb goes into the lampholder, whether it fits inside the shade and whether it is in proportion with the fitting. In this category the catalogue is sorted by bulb shape and diameter, from small LED bulbs such as A60, G45 and C37 to large LED bulbs like G125, G250 and T220, taking in the mid-size G80, G95, ST64 and T178 along the way.

How to read the code: a letter plus a number

Every bulb is identified by a combination of letter and number. The letter describes the shape of the bulb and the number is its maximum diameter in millimetres:

• A: standard pear shape. An A60 measures 60 mm across.
• G: globe or golf ball. G45 is 45 mm; G125, 125 mm.
• C: candle. The C37 is the typical bulb for multi-arm fittings.
• ST: straight tubular Edison, with an elongated body and a pronounced shoulder. The ST64 measures 64 mm across.
• T: long tubular. The T178 and T220 are very slender pieces for pendant lights.

With that rule you can decode any reference without looking up a table: the letter tells you the silhouette and the number tells you how wide it will be.

Small, medium and large: what each group is for

• Small (A60, G45, C37): the standard replacement for the home. They fit in enclosed flush mounts, wall lights, bedside lamps and multi-arm fittings, where interior space is tight.
• Medium (G80, G95, ST64, T178): the territory of bulbs on show. They have enough presence to look good in a pendant without being out of scale in a normal room.
• Large (G125, G250, T220): large format pieces for high ceilings, stairwells, long tables and hospitality venues. They work as the main decorative element.

Why size matters before you buy

There are two practical reasons. The first is fit: in enclosed flush mounts, glass shades and narrow wall lights, a few extra millimetres stop the shade from closing or leave the bulb touching the glass. The second is visual proportion: in a pendant, a bulb that is too small gets lost in the fitting and one that is too big overwhelms the rest of the design. As a guide, the higher the light point and the wider the surface it lights, the larger the diameter can be. Keep the base in mind too: large formats usually come in E27, while C37 candles and G45 golf balls are common in E14.

How to measure the space you have

Before choosing, spend a minute measuring. With the light off and the bulb cool, take out the current bulb and take two measurements with a tape measure: the clear width at the narrowest point of the shade or recess, and the available height from the mouth of the lampholder to the back or the rim. Compare the width with the number in the code (a G95 needs at least 95 mm clear plus some slack) and leave a few millimetres on each side so air can circulate. If you still have the old bulb to hand, simply measure its diameter at the widest point and its overall length: that is the most reliable reference of all.

Measure, identify the code and filter by size at FactorLED: we have small, medium and large LED bulbs in E27 and E14 bases, with the colour temperature you need and the 15,000 to 25,000 hour service life that comes with LED. Get the right size first time and avoid returns.

Frequently asked questions about LED bulb sizes

What do A60 or G95 mean on a bulb?

The letter indicates the shape of the bulb and the number its diameter in millimetres. A60 is a standard pear shaped bulb 60 mm wide, and G95 is a globe of 95 mm.

Which are the most common small LED bulbs?

The standard A60, the G45 golf ball and the C37 candle. They are the ones that fit in enclosed flush mounts, wall lights and multi-arm fittings, and the most frequent choice as a household replacement.

How do I measure whether the bulb fits my light fitting?

Measure the clear width at the narrowest point of the shade and the height from the lampholder to the rim. The bulb diameter is the number in its code, and it is worth leaving a few millimetres of slack for ventilation.

Which large LED bulb size should I choose for a pendant?

It depends on ceiling height and the surface you need to cover. The G125, G250 and T220 formats are designed for high ceilings, long tables and commercial venues; in a standard room, a G95 or an ST64 usually keeps better proportion.