Light Bulb Base Chart
E26, E27, GU10, bayonet.
E26, E27, GU10, bayonet.
How to use Light Bulb Base Chart
- Pick a bulb base code like E26, GU10, or B22
- Read its thread or pin size, common name, and voltage
- Check which bases it can and can't swap with
About Light Bulb Base Chart
Light bulb bases come in dozens of codes, and the wrong one either won't fit the socket or won't run at your mains voltage. This chart lets you pick a base — E26, E27, E12, E14, B22, GU10, GU5.3 and more — and instantly see its size, common name, typical voltage, and where it's normally used, so you can order the right replacement the first time.
For a sizes chart, the number in a screw ('E', Edison) code is simply the thread diameter in millimetres: E12 is 12 mm (candelabra), E14 is 14 mm (small Edison), E26 is 26 mm (US medium) and E27 is 27 mm (European medium). For a types chart, it also covers the other families — bayonet ('B') bases that push in and twist a quarter-turn, and pin bases like GU10 and GU5.3 — with the pin spacing that tells them apart.
The part that trips people up is interchangeability. Some bases look identical but differ in voltage (E26 vs E27) or don't swap at all (GU10 vs GU5.3), and the chart flags which bases can and can't stand in for each other, so you don't fit a 12 V bulb where 230 V is needed. It's completely free with no sign-up, and it runs entirely in your browser — nothing is uploaded.
Frequently asked questions
- What are the standard light bulb base sizes?
- For screw bases the code is the diameter in millimetres: E12 is 12 mm (candelabra), E14 is 14 mm (small Edison), E26 is 26 mm (US medium) and E27 is 27 mm (European medium). Bayonet and pin bases use their own numbering — B22 is 22 mm across, while GU10 and GU5.3 are named for their 10 mm and 5.3 mm pin spacing.
- What are the different types of light bulb bases?
- There are three main families: screw ('E', Edison) bases that thread into the socket, bayonet ('B') bases that push in and twist a quarter-turn to lock, and pin bases such as GU10 (twist-lock) and GU5.3 (push-in). The chart groups each code by type so you can see which family a bulb belongs to before you buy.
- How do I identify my light bulb base?
- Measure the base: for screw (Edison, 'E') bases the number is the diameter in millimetres — E14 is 14 mm, E27 is 27 mm. Bayonet ('B') bases push in and twist. The chart lists each with its size and common name so you can match what you have.
- What is the difference between E26 and E27?
- Both are 'medium' Edison screw bases and physically fit each other's sockets — E26 is 26 mm (US, 120 V) and E27 is 27 mm (Europe/UK, 230 V). The catch is voltage, so match the bulb to your mains rather than assuming they're identical.
- What size is an E12 or E14 base?
- E12 measures 12 mm across the screw thread and is usually called candelabra, common in chandeliers and small lamps. E14 is 14 mm, the small Edison screw used widely in Europe. Measure the widest part of the metal base in millimetres and match it to the code.
- Are GU10 and GU5.3 bulbs interchangeable?
- No. They look similar but GU10 is a mains-voltage (230 V) twist-lock base, while GU5.3 (MR16) is a 12 V push-in base that needs a transformer — using the wrong one won't work and isn't safe.
- What is a B22 bulb base?
- B22 is the bayonet cap (BC), the 22 mm push-and-twist base that's standard in the UK, Australia and much of the Commonwealth — the bayonet equivalent of the E27 screw base.
- What's the difference between screw and bayonet bulbs?
- Screw (Edison, 'E') bulbs twist into a threaded socket; bayonet ('B') bulbs push in and twist a quarter-turn to lock onto two pins. They're not interchangeable without an adapter.
- What is the most common light bulb base?
- In North America the E26 medium Edison screw is the standard household base; in Europe it's the E27 screw, and in the UK, Australia and much of the Commonwealth the B22 bayonet cap. Smaller E12 and E14 screws are common in decorative and lamp fittings.
- Is there a light bulb base chart PDF?
- You can use this chart free on the page as a printable reference — bookmark it or print the page, and it works the same on a phone or desktop, with no download or sign-up. Look up any base code, its size and voltage right here whenever you need it.