What is the Standard Light Bulb Size? [A Quick Guide]

When people say “this light takes a standard bulb” or “this light takes the standard light bulb size”, it’s assumed you know what that size is.

Is there a standard bulb size worldwide? Does it not differ per country?

Let’s have a look.

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Quick Links

What is the standard light bulb size?
What about the A19/A60 bulb?
Are E26 and E27 bulbs the same?
- The more technical reason
Are E26 and E27 LED bulbs interchangeable?
Frequently asked questions
- What voltage do LED bulbs work at?
- What does E27 mean on a light bulb?

What is the standard light bulb size?

The standard light bulb size in most countries is the E26 or E27 bulb.

These are the standard screw-in bulb bases used in North America (E26) and European countries (E27). The “E” stands for Edison, named after Thomas Edison, who popularized the incandescent light bulb.

These bulbs have a medium screw base and are used for a wide range of lighting fixtures from recessed lighting to floor lamps, to pendant lights – you name it.

What about the A19/A60 bulb?

While A19 bulbs are also considered a ‘standard’ bulb size, this simply refers to the glass part of the bulb. All A19 and A60 bulbs use an E26 and/or E27 base, depending on whether you’re in North America or Europe.

The ‘A’ refers to the shape of the glass – the classic upside-down pear shape you think of when you imagine a light bulb.

The 19 or 60 part refers to the width of the glass at its widest point. Both the A19 and A60 are actually exactly the same, it’s just that in North America it’s measure in eights of an inch, whereas in Europe (and the rest of the world) it’s measured in millimetres.

So, an A19 bulb is 19/8 inches (2.4 inches), which is 60mm.

Are E26 and E27 bulbs the same?

While incredibly similar, E26 and E27 bulbs are not exactly the same.

They are the same size, so you could screw an E26 bulb into an E27 lampholder and vice-versa.

However, E26 bulbs are for use in North America where the electricity supply runs at 120V, whereas E27 bulbs are for use in Europe where the electricity runs as 240V.

In practice, this means that you can safely use an E27 bulb in an E26 lampholder, because the E27 bulb is designed to accept voltages up to 240V, while North American electricity supplies only go up to half of that at 120V, meaning they’ll work fine.

You cannot use an E26 bulb in an E27 lampholder, however. An E26 bulb is designed to accept voltages up to 120V, but the European electricity supply runs at double that (240V).

Therefore, if you try to put an E26 bulb in an E27 bulb holder, while it will fit just fine, it will pose a huge safety hazard, shorting out the bulb and potentially starting a fire.

The more technical reason

While the above explanation is correct, it only gives a broad explanation as to why you can’t use an E26 bulb in an E27 bulb holder.

To be more specific, the higher voltage a light bulb is expected/designed to receive, the wider apart the live and neutral contacts need to be.

So, because an E26 bulb expects a lower voltage to be supplied, it’s live and neutral contacts can safely be closer than they can on an E27 bulb.

Are E26 and E27 LED bulbs interchangeable?

Yes. Old incandescent light bulbs only ran at a specific voltage. In North America, they decided to use 120V. In Europe, they decided to use 240V.

This meant that North American E26 bulbs and European E27 bulbs were not meant to be interchangeable (even though you could still technically use an E26 bulb in an E27 lampholder, as explained above).

When LED bulbs were developed however, they didn’t have to work solely on one single voltage – instead, you could design them to work within a range of voltages.

This meant that LED bulbs could be designed to work at 120V-240V (sometimes 90V-260V), meaning they could be used at both the 120V and 240V levels.

Frequently asked questions

What voltage do LED bulbs work at?

All LED bulbs work at a very low voltage, usually 12-24V DC. However, modern LED bulbs will come with a driver that converts this low voltage direct current electricity into higher voltage AC current that we use in our homes.

So while LED bulbs work at only 12-24V DC, they will have a driver installed to allow them to work at 120V AC (if you’re in North America) or 240V AC (if you’re in Europe).