LED Bulb Base Types Explained – Find the Right Fit for Your Fixture
Understand E27, B22, E14, GU10 and more so you can match every LED bulb to its perfect fitting with confidence.
When buying a new LED bulb, the base — also called the socket or cap — matters just as much as the shape or brightness. Choosing the correct base ensures the bulb fits safely and works efficiently with your fixture. This guide explains the most common LED bulb bases in Australia, what the codes mean, and where to use them.
Quick-reference base types and dimensions for Australian fixtures.
Overview: Common LED Base Types & Sizes
| Base | Type | Size / Spacing | Voltage | Typical Use |
|---|---|---|---|---|
| E27 | Edison screw | 27 mm Ø | 240 V | Standard lamps, pendants, decorative globes |
| E14 | Small Edison screw | 14 mm Ø | 240 V | Candle/golf-ball bulbs, chandeliers, small lamps |
| E12 | Candelabra Edison screw | 12 mm Ø | 240 V | Chandeliers, imported decorative fittings |
| B22 | Bayonet cap (push & twist) | 22 mm Ø | 240 V | Ceiling lights & lamps in most AU homes |
| B15 | Small bayonet cap | 15 mm Ø | 240 V | Chandeliers, ornamental or vintage fixtures |
| GU10 | Twist-lock bi-pin | 10 mm pin pitch | 240 V | Downlights, spotlights (mains) |
| GU5.3 (MR16) | Bi-pin | 5.3 mm pin pitch | 12 V | Recessed downlights with transformer |
| G4 | Bi-pin | 4 mm pin spacing | 12 V | Under-cabinet, display, RV/boat, small fixtures |
| G9 | Loop-pin bi-pin | 9 mm pin spacing | 240 V | Compact decorative fittings, wall lights, pendants |
E27 — Edison Screw (27 mm)
The most common bulb base in Australia. It features a simple screw-in mechanism and is found in most lamps and pendant fittings. E27 LED bulbs are ideal replacements for traditional incandescent bulbs.
- Size: 27 mm diameter screw cap.
- Note: Use AU-rated E27 bulbs (240 V). E26 bulbs from the US look similar but are 120 V and not suitable here.
E14 — Small Edison Screw (14 mm)
A smaller screw base used for decorative or compact bulbs like candles and golf balls. Common in chandeliers, wall lights, and bedside lamps.
- Size: 14 mm diameter.
- Common in: Decorative and space-saving fittings.
E12 — Candelabra Edison Screw (12 mm)
Often seen on imported or American-style chandeliers. It’s slightly smaller than E14 and common in candelabra fixtures and ornate lamps.
- Size: 12 mm diameter.
- Tip: Always confirm the fitting size before ordering — E12 and E14 are visually similar but not interchangeable.
B22 — Bayonet Cap (22 mm)
The classic “push-and-twist” fitting used throughout Australian homes. Reliable, secure, and easy to install. Ideal for general lighting, lamps, and pendants.
- Size: 22 mm diameter with twin locking pins.
- Common in: Ceiling and wall fixtures, lamps, older fittings.
B15 — Small Bayonet Cap (15 mm)
The smaller version of the B22, used in decorative fittings like chandeliers and sconces. Features the same push-and-twist lock mechanism.
- Size: 15 mm diameter.
- Common in: Heritage or ornamental fixtures where bulb size matters.
GU10 — Twist-Lock (Mains 240 V)
Found in most modern downlights and track lighting. GU10 bulbs connect directly to mains power with a quarter-turn twist-lock base — no driver required.
- Pin spacing: 10 mm with locking lugs.
- Used for: Ceiling downlights, accent lighting, and spotlights.
GU5.3 (MR16) — 12 V Bi-Pin
Common in low-voltage recessed fittings, often installed with a transformer. Ideal for accent or task lighting where bright, focused light is needed.
- Pin spacing: 5.3 mm between pins.
- Voltage: 12 V (requires LED-compatible transformer).
G4 — Bi-Pin (12 V Compact)
Small capsule bulbs used in tight or intricate fittings. Perfect for under-cabinet, display, or caravan lighting.
- Pin spacing: 4 mm between pins.
- Voltage: 12 V (low-voltage driver required).
G9 — Loop-Pin (240 V)
Compact capsule bulbs for decorative wall and pendant fittings. G9 LEDs run directly on mains power and offer bright, even light in a small form.
- Pin spacing: 9 mm.
- Used for: Pendants, wall lights, and small decorative fittings.
Choosing the Right Base: Quick Checklist
- 1) Check your fitting: Look for the base code (E27, B22, GU10, etc.) printed on the socket or old bulb.
- 2) Match voltage: Mains fittings use 220–240 V; G4, G5.3/MR16 use 12 V.
- 3) Confirm the cap size: E12, E14, E27 and B15, B22 are not interchangeable.
- 4) Select colour temperature: 2000–2200 K (extra warm) for ambience, 2700–3000 K for general use, 4000 K for clarity.
- 5) Choose lumens, not watts: 400–800 lm suits most living spaces.
FAQs
What’s the difference between E27 and B22 bases?
E27 is a screw cap (27 mm) you twist in; B22 is a bayonet cap (22 mm) that pushes in and twists to lock. They’re not interchangeable. Use the base type that matches your fitting for the best safety and fit. Adapters exist, but a like-for-like base is more reliable.
What’s the difference between E12 and E14 bases?
Both are screw caps used in small fittings. E12 is 12 mm (often on imported candelabras), while E14 is 14 mm and more common locally. They look similar but are different sizes — check the marking on your old bulb or socket before ordering.
Shop LED Bulbs by Base
- E27 (Edison Screw)
- E14 (Small Edison Screw)
- E12 (Candelabra Base)
- B22 (Bayonet Cap)
- B15 (Small Bayonet)
- GU10 (Mains 240 V)
- GU5.3 / MR16 (12 V)
- G9 (Mains 240 V)
- G4 (12 V)
If you’re not sure which base your fixture needs, send a quick photo through our Contact Us page — we’ll help you find the right fit.