Light Bulb Fittings Explained: BC, ES, SES, GU10 and G9

Most of our lamps and light fittings are sold without a bulb, so it helps to know which one to buy. This guide explains the common UK bulb fittings and how to choose the right LED bulb.

What do the bulb fitting letters mean?

The letters describe the cap, the part of the bulb that connects to the lamp. The number is the width of the cap in millimetres.

• BC or B22 (bayonet cap): the traditional UK push and twist fitting, 22mm wide with two side pins.
• ES or E27 (Edison screw): a 27mm screw fitting, now very common on lamps and ceiling lights.
• SES or E14 (small Edison screw): a 14mm screw fitting, used on smaller table lamps, wall lights and chandeliers.
• SBC or B15 (small bayonet cap): a 15mm version of the bayonet fitting.
• GU10: a spotlight bulb with two thick pins that push in and twist to lock.
• G9: a small capsule bulb with two looped pins, often used in compact decorative fittings.

Every Happy Homewares product description states the fitting, for example: requires 1 x 40 watt SES (E14) bulb.

How bright should the bulb be?

Brightness is measured in lumens, not watts. LED bulbs give the same light as old filament bulbs while using a fraction of the power.

• An old 40 watt bulb gives about 470 lumens.
• An old 60 watt bulb gives about 800 lumens.
• An old 100 watt bulb gives about 1,500 lumens.

Look for the lumens figure on the bulb box and choose the brightness you want.

What is the maximum wattage?

Each fitting and shade has a maximum wattage, given in the product description. Always stay within it. Some fittings are designed for LED bulbs only and say so in the description.

Warm white or cool white?

The colour of light is measured in kelvins (K). Warm white, around 2700K, gives a cosy yellowish light that suits living rooms and bedrooms. Cool white, around 4000K, is crisper and suits kitchens, bathrooms and work areas. Daylight bulbs, around 6500K, give a bluish white light.

Can I use a dimmer?

Many of our fittings are suitable for dimming, as long as the bulb is dimmable too. Check that the bulb box says dimmable, and note that LED bulbs work best with a dimmer switch designed for LEDs.

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