The Complete Guide to Light Bulbs: Sizes, Shapes & Lamp Holder Fittings Explained
Choosing the right light bulb can be confusing. With names like E27, GU10, G9, A60 and ST64, it's easy to wonder which bulb fits your light fitting and what all these codes actually mean.
Whether you're replacing an old globe or choosing bulbs for a brand-new light fitting, understanding the different bulb shapes, sizes and lamp holder types will help you get the best performance, appearance and energy efficiency.
This guide explains everything you need to know about modern LED light bulbs, including common fittings, bulb shapes and colour temperatures.
Why Bulb Codes Matter
Every light bulb has two important characteristics:
- The lamp holder (base) – how the bulb connects to the light fitting.
- The bulb shape – the appearance and size of the bulb.
For example:
E27 A60
means:
- E27 = Edison Screw base
- A60 = Standard pear-shaped bulb measuring approximately 60 mm in diameter
Understanding Lamp Holder Types
E27 (Edison Screw)
The most common household bulb.
Diameter: 27 mm
Commonly used for:
- Ceiling lights
- Pendant lights
- Floor lamps
- Table lamps
- Outdoor lights
Best for
General household lighting.
E14 (Small Edison Screw)
Smaller version of E27.
Diameter: 14 mm
Commonly found in:
- Chandeliers
- Decorative lamps
- Wall lights
- Bedside lamps
Ideal where a compact bulb is needed.
GU10
GU10 bulbs use two pins with a twist-and-lock fitting.
Commonly used in:
- Downlights
- Spotlights
- Track lighting
- Kitchen lighting
These are among the most popular LED spotlight bulbs.
G9
G9 bulbs feature two loop pins spaced 9 mm apart.
Often used in:
- Decorative wall lights
- Pendant lights
- Modern chandeliers
- Bathroom fittings
Because they're compact, they're ideal for small decorative fittings.
B22 (Bayonet)
A traditional push-and-twist fitting.
Although less common in modern homes, many older South African properties still use B22 fittings.
MR16
MR16 bulbs have two straight pins and are typically used with low-voltage lighting systems.
Often found in:
- Landscape lighting
- Cabinet lighting
- Display lighting
Understanding Bulb Shapes
A Series (Standard Bulbs)
The classic household bulb.
Examples:
- A60
- A67
- A70
Perfect for:
- Table lamps
- Floor lamps
- Ceiling fittings
Globe Bulbs
Larger round bulbs designed to be seen.
Popular sizes:
- G80
- G95
- G125
Perfect for:
- Pendant lights
- Decorative fittings
- Open bulb fixtures
Candle Bulbs
Slim elegant bulbs that resemble candle flames.
Available in:
- Straight candle
- Bent tip candle
- Flame tip candle
Most commonly used in:
ST Bulbs
Vintage Edison-style bulbs.
Example:
ST64
These expose decorative LED filaments and are ideal for:
- Industrial lighting
- Café interiors
- Pendant lights
Tubular Bulbs
Long narrow bulbs used where a slim profile is needed.
Common examples:
- T30
- T45
Suitable for:
Golf Ball Bulbs
Compact spherical bulbs.
Examples:
- G45
Perfect for:
- Small lamps
- Decorative fittings
- Bathroom lights
LED Filament Bulbs
LED filament bulbs combine vintage style with modern efficiency.
Advantages include:
✓ Lower electricity consumption
✓ Long lifespan
✓ Instant brightness
✓ Decorative appearance
Choosing the Right Colour Temperature
Warm White (2700K–3000K)
Perfect for:
- Living rooms
- Bedrooms
- Dining rooms
Creates a warm, relaxing atmosphere.
Cool White (4000K)
Ideal for:
- Kitchens
- Bathrooms
- Laundry rooms
Provides crisp, practical lighting.
Daylight (5000K–6500K)
Best for:
- Workshops
- Garages
- Commercial spaces
Produces bright, high-clarity illumination.
Dimmable vs Non-Dimmable Bulbs
If your light fitting uses a dimmer switch, you'll need a dimmable LED bulb.
Using a non-dimmable bulb on a dimmer may result in:
- Flickering
- Buzzing
- Reduced bulb life
Always check both the bulb and dimmer compatibility.
Quick Bulb Selection Guide
| Light Fitting | Most Common Bulb |
|---|---|
| Ceiling Light | E27 A60 |
| Pendant Light | E27 G95 |
| Chandelier | E14 Candle |
| Wall Light | G9 or E14 |
| Downlight | GU10 |
| Table Lamp | E27 A60 |
| Floor Lamp | E27 A60 |
| Decorative Pendant | ST64 |
Frequently Asked Questions
What is the difference between E27 and E14?
Both are Edison Screw bulbs. E27 has a 27 mm screw base, while E14 has a smaller 14 mm base typically used in decorative fittings.
Can I use an LED bulb in an older light fitting?
Yes, provided the lamp holder type matches and the fitting is compatible with LED bulbs.
Are larger bulbs brighter?
Not necessarily. Brightness is measured in lumens, not bulb size.
What does A60 mean?
"A" refers to the classic pear-shaped bulb, while "60" indicates the approximate diameter in millimetres.
What does G95 mean?
"G" stands for globe, and "95" refers to the bulb's diameter in millimetres.
Find the Perfect Bulb at Elevenpast
Choosing the right bulb doesn't have to be confusing. Once you understand bulb shapes, sizes and lamp holder types, it's much easier to select the perfect option for your light fitting.
At Elevenpast, you'll find a wide range of LED bulbs, decorative filament bulbs and replacement globes designed to suit everything from modern pendant lights to classic chandeliers and everyday household lighting.