Choosing the correct light bulb isn’t just about brightness; it also means selecting the right shape, size, and base for your fixture. Light bulb codes such as A19, BR30, PAR38, MR16, and T8 indicate the bulb’s shape and diameter, making it easier to find a compatible replacement.
This light bulb size chart explains the most common bulb types, their dimensions, and where they’re typically used so you can choose the right bulb with confidence.
Most Popular Light Bulb Sizes (US and UK)
| BULB series | CODE | DIAMETER IN (Inches and mm) | LENGTHS IN (inches and mm) |
| A Series | A19 (US) or A6 (UK) | 60 mm 2.4 inches | 3.9 – 4.3 inches (99.06 – 110 mm) |
| B Series | B10 | 31.75 mm 1.3 inches | 3.5 – 4.4 inches (90 -113 mm) |
| C Series | C9 | 28.58 mm 1.1 inches | 3.5 – 3.9 inches (90 – 100 mm) |
| CA Series | CA10 | 31.75 mm 1.3 inches | 3.5 – 3.9 inches (90 – 100 mm) |
| R Series | R50 | 159 mm 6.3 inches | 3.4 inches (86 – 87 mm) |
| R Series | R63 | 200 mm 7.9 inches | 3.9 – 4.0 inches (100 – 102 mm) |
| R/BR Series | R80 | 254 mm 10 inches | 4.4 – 4.8 inches (112 – 118 mm) |
| PAR Series | PAR16 | 50.8 mm 2 inches | 2.0 – 2.2 inches (50 – 55 mm) |
| PAR Series | PAR20 | 63.5 mm 2.5 inches | 2.5 – 8.9 inches(64 -89 mm) |
| AR Series | PAR36 | 111 mm 4.4 inches | 2.3 – 2.6 inches (58 – 66 mm) |
| PAR Series | PAR36 | 120.65 mm 4.8 inches | 5.3 – 5.4 inches (134 – 136 mm) |
| MR Series | MR11 | 35 mm 1.4 inches | 1.5 – 1.7 inches (37 42 mm) |
| MR Series | MR16 | 50.8 mm 2 inches | 1.8 – 2.1 inches (45 – 53 mm) |
| G Series | G25 (US) or G80 (UK) | 80 mm 3.2 inches | 120 mm 4.7 inches |
| G Series | G30 (US) or G95 (UK) | 95 mm 3.7 inches | 140 mm 5.5 inches |
| G Series | G40 (US) or G125 (UK) | 125 mm 4.9 inches | 6.5 – 6.7 inches(165 – 170 mm) |
| T Series | T30 | 30 mm 1.2 inches | 8.9 – 11.8 inches (225 – 300 mm) |
| T Series | T45 | 45 mm 1.8 inches | 110 mm 4.3 inches |
| T Series | T5 | 16 mm 0.6 inches | 12.0 – 57.6 inches (305 -1463 mm) |
| T Series | T8 | 26 mm 1.0 inches | 13.0 – 48.0 inches (330 – 1220 mm) |
Light Bulb Sizes – Shapes, and Codes
A Series.
| Description | Measurement |
|---|---|
| Common Lengths | 3.9 – 4.3 inches (100 – 110 mm) |
| Diameter | 60 mm (2.3622 inches) |
| Light Bulb Code | A19 (US) or A60 (UK) |
| Diameter (1/8th inch) | 2 3/8″ (10/8 diameter) |
B/C/CA Series
| Category | B10 | C9 | CA10 |
|---|---|---|---|
| Common Lengths | 90 – 113 mm (3.5 – 4.4 inches) | 90 – 100 mm (3.5 – 3.9 inches) | 110 – 130 mm (4.3 – 5.1 inches) |
| Diameter | 31.75 mm (1.3 inches) | 28.58 mm (1.1 inches) | 31.75 mm (1.3 inches) |
| Diameter (1/8th inch) | 10/8 (1 1/4″) | 9/8 (1 1/8″) | 10/8 (1 1/4″) |
R and BR Series
| Category | R50 | R63 | R80 |
|---|---|---|---|
| Light Bulb Code | R50 | R63 | R80 |
| Common Lengths | 86 – 87 mm (3.4 inches) | 100 – 102 mm (3.9 – 4.0 inches) | 112 – 118 mm (4.4 – 4.6 inches) |
| Diameter | 159 mm (6.3 inches) | 200 mm (7.9 inches) | 254 mm (10 inches) |
| Diameter (1/8th inch) | 50/8 (6 1/4″) | 63/8 (7.86″) | 80/8 (10″) |
MR Series.
| Category | MR11 | MR16 |
|---|---|---|
| Light Bulb Code | MR11 | MR16 |
| Common Lengths | 50 – 55 mm (2.0 – 2.2 inches) | 64 – 89 mm (2.5 – 3.5 inches) |
| Diameter | 50.8 mm (2 inches) | 63.5 mm (2.5 inches) |
| Diameter (1/8th inch) | 16/8 (2″) | 20/8 (2.5″) |
G Series
| Category | G25 (US) / G80 (UK) | G30 (US) / G95 (UK) |
|---|---|---|
| Light Bulb Code | G25 (US) / G80 (UK) | G30 (US) / G95 (UK) |
| Common Lengths | 120 mm (4.7 inches) | 140 mm (5.5 inches) |
| Diameter | 80 mm (3.1 inches) | 95 mm (3.7 inches) |
| Diameter (1/8th inch) | 25/8 (3.14”) | 30/8 (3.70”) |
T Series
| Category | T30 | T45 |
|---|---|---|
| Light Bulb Code | T30 | T45 |
| Common Lengths | 225–300 mm (8.9–11.8 inches) | 110 mm (4.3 inches) |
| Diameter | 30 mm (1.2 inches) | 45 mm (1.8 inches) |
| Diameter (1/8th inch) | 1.18” | 1.77” |
AR and PAR Series
| Category | PAR16 | PAR20 |
|---|---|---|
| Light Bulb Code | PAR16 | PAR20 |
| Common Lengths | 50–55 mm (2.0–2.2 inches) | 64–89 mm (2.5–3.5 inches) |
| Diameter | 50.8 mm (2 inches) | 63.5 mm (2.5 inches) |
| Diameter (1/8th inch) | 16/8 (2″) | 20/8 (2.5″) |
Understanding Light Bulb Size Codes
Light bulb model numbers usually consist of letters and numbers.
- Letter = bulb shape
- Number = maximum diameter
For example:
- A19
- BR30
- PAR38
- MR16
- T8
The number generally represents the diameter in eighths of an inch for US bulb codes.
For example:
- A19 ≈ 19/8 inches (about 2.4 inches)
- BR30 ≈ 30/8 inches
- PAR38 ≈ 38/8 inches
Understanding these codes makes replacing bulbs much easier.
Importance of Choosing the Right Light Bulb Size
Selecting the correct light bulb size is crucial for achieving the desired lighting effect and ensuring compatibility with your fixtures. On one hand, choosing the right size guarantees that the bulb fits perfectly and performs optimally. On the other hand, selecting the wrong size can lead to inadequate lighting or even damage your fixtures.
Balancing factors like bulb dimensions and fixture requirements is essential. By carefully considering these details, you enhance both the functionality and aesthetics of your space, ensuring that your lighting setup meets your needs effectively.
Common Light Bulb Sizes and Types
A-Series Bulbs
The A-series is the most common household bulb shape.
Popular sizes include:
- A15
- A19
- A21
Typical uses:
- Table lamps
- Ceiling fixtures
- Floor lamps
- Bedrooms
- Living rooms
A19 is the standard household light bulb used in most homes.
B-Series Bulbs
B-series bulbs feature a decorative bullet or torpedo shape.
They’re commonly used in:
- Chandeliers
- Wall sconces
- Decorative fixtures
They provide elegant styling rather than maximum brightness.
C and CA Bulbs
These candle-shaped bulbs are designed for decorative lighting.
Common applications include:
- Dining room chandeliers
- Pendant lighting
- Wall lights
- Decorative lamps
PAR Bulbs
PAR (Parabolic Aluminized Reflector) bulbs create a focused beam of light.
Common sizes include:
- PAR16
- PAR20
- PAR30
- PAR38
Typical uses:
- Outdoor lighting
- Floodlights
- Track lighting
- Recessed ceiling lights
BR and R Bulbs
BR (Bulged Reflector) and R (Reflector) bulbs produce a wider beam than PAR bulbs.
They’re commonly used for:
- Recessed lighting
- Ceiling cans
- Indoor floodlights
MR Bulbs
MR bulbs are compact reflector bulbs frequently used for accent lighting.
Popular options:
- MR11
- MR16
Common applications:
- Landscape lighting
- Display cabinets
- Track lighting
G-Series Bulbs
G-series bulbs have a round globe shape.
Popular models include:
- G25
- G30
- G40
They’re commonly used around:
- Bathroom mirrors
- Vanity lighting
- Decorative fixtures
T-Series Bulbs
T-series bulbs have a tubular design.
Examples include:
- T5
- T8
- T12
These are commonly found in:
- Fluorescent fixtures
- Garages
- Offices
- Commercial buildings
How to Choose the Right Light Bulb
Before buying a replacement bulb, check:
✅ Bulb shape
✅ Bulb diameter
✅ Base type
✅ Wattage
✅ Brightness (Lumens)
✅ Color temperature
Choosing the correct size ensures the bulb fits properly and performs as expected.
Where to Find the Bulb Size
You can usually find the bulb code:
- Printed on the bulb
- On the original packaging
- Inside the light fixture
- In the fixture owner’s manual
If the code isn’t visible, measure the bulb and compare it with a sizing chart.
LED vs Traditional Bulb Sizes
LED bulbs use the same sizing system as incandescent bulbs.
For example:
- LED A19 replaces incandescent A19.
- LED BR30 replaces incandescent BR30.
- LED PAR38 replaces halogen PAR38.
The physical dimensions remain nearly identical, while energy consumption is significantly lower.
Tips Before Buying
- Check the fixture’s maximum wattage.
- Verify the bulb base matches the socket.
- Choose the correct color temperature.
- Use damp-rated or outdoor-rated bulbs where required.
- For dimmable fixtures, purchase dimmable bulbs.
Conclusion
Light bulb size codes may seem confusing at first, but understanding the letters and numbers makes choosing a replacement much easier. Whether you’re replacing a standard A19, a decorative G25, or a directional PAR38, selecting the correct size ensures proper fit, safe operation, and the lighting performance you expect.
Always verify the bulb shape, dimensions, and base type before purchasing to ensure compatibility with your fixture.
FAQs
1. What does A19 mean on a light bulb?
The letter A refers to the standard pear-shaped bulb, while 19 indicates a diameter of 19 eighths of an inch, or approximately 2.4 inches.
2. What’s the most common household light bulb size?
The A19 is the most common light bulb used in homes for lamps, ceiling fixtures, and general lighting.
3. Are LED bulbs the same size as incandescent bulbs?
Yes. LED replacement bulbs typically use the same size and shape codes as incandescent and halogen bulbs, making them compatible with most existing fixtures.
4. What’s the difference between BR30 and PAR30 bulbs?
BR30 bulbs produce a wider, softer beam, while PAR30 bulbs provide a more focused and directional light, making them better for accent and spotlighting.
5. Can I use a different bulb size in my fixture?
Only if the fixture allows it. Using the wrong bulb size may prevent proper installation or affect light distribution and safety.
6. How do I know which light bulb fits my fixture?
Check the existing bulb’s code, the fixture label, or the owner’s manual. If you’re unsure, measure the bulb and compare it with a light bulb size chart.
7. What are G25 bulbs used for?
G25 globe bulbs are commonly used in bathroom vanity lights, decorative fixtures, and makeup mirrors because of their round shape and even light output.
8. What does the number on a light bulb represent?
For most US bulb codes, the number represents the bulb’s maximum diameter in eighths of an inch. For example, a BR30 bulb measures approximately 30/8 inches (3.75 inches) in diameter.