Light Bulb Base Chart
E26, E27, GU10, bayonet.
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About Light Bulb Base Chart
Identify any light bulb base and see its type, size and where it's used. Pick a code — E26, E27, E12, E14, B22, GU10, GU5.3 and more — and get the thread or pin diameter, the common name, the typical voltage, and which bases it can (and can't) be swapped with.
Some bases look identical but differ in voltage (E26 vs E27) or aren't interchangeable at all (GU10 vs GU5.3), which is exactly where people get caught out. It is completely free with no sign-up, and it runs entirely in your browser.
Frequently asked questions
- 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.
- 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.
- 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.