Lighting & Bulbs · 7 min read · Beginner

UK Light Bulb Fittings Explained: E27, E14, B22, B15 & GU10

Identify the common UK lamp-cap types by shape and code so you can buy a compatible replacement bulb without forcing the wrong fitting.

Key points & steps

Switch the light off and allow the lamp to cool before removing it. For portable lamps, unplug them before changing the bulb.
Read the code printed on the old lamp or fitting where available. Common UK replacements include E27, E14, B22, B15 and GU10.
E27 is the larger Edison screw base, commonly around 27mm in diameter. E14 is the smaller Edison screw commonly used in compact lamps and chandeliers.
B22 is the familiar standard UK bayonet cap with two side pins. B15 is a smaller bayonet version used in some compact fittings.
GU10 lamps have two short lugs/pins and normally lock into mains-voltage spotlight fittings with a push-and-twist action.
Match the cap type first, then check the bulb shape, physical dimensions, voltage, dimming compatibility and the fitting manufacturer’s maximum rating.
Never force a lamp into a holder. A replacement should fit positively and match the fitting’s intended cap type.

Similar-looking bulbs can use different bases, so take the old lamp or a clear photo of the markings when buying a replacement.
Integrated LED fittings may not have a replaceable bulb at all; if the LED module or driver has failed, follow the fitting manufacturer’s repair/replacement guidance.
If a lampholder is scorched, cracked, loose, corroded or shows signs of overheating, do not simply fit another bulb—have the fitting checked.