AR20, PAR30, and PAR38 lamps are all directional reflector lamps, but they differ mainly in diameter, physical size, light output, beam options, and typical fixture/application size.
The number in the PAR designation represents the bulb’s diameter in eighths of an inch. That makes the nominal diameters:
- PAR20: 20/8 = 2.5 inches
- PAR30: 30/8 = 3.75 inches
- PAR38: 38/8 = 4.75 inches
Current LED manufacturer specifications are very close to those nominal sizes, with typical PAR20 lamps around 2.5 inches, PAR30 around 3.7–3.75 inches, and PAR38 around 4.7–4.75 inches in diameter.
PAR20 vs PAR30 vs PAR38 at a Glance
| Feature | PAR20 | PAR30 | PAR38 |
|---|---|---|---|
| Nominal diameter | 2.5 in. | 3.75 in. | 4.75 in. |
| Relative size | Small | Medium | Large |
| Typical use | Accent, track, smaller recessed fixtures | Recessed, track, retail/display lighting | High-output recessed, flood, exterior and commercial applications |
| Beam options | Spot to flood | Spot to flood | Spot to wide flood |
| Common base | E26 on many models | E26 on many models | E26 on many models |
| Replacement priority | Match fit and beam | Match fit, neck length and beam | Match fit, beam, output and environment |
Important: the PAR size alone does not tell you whether one lamp is a correct replacement for another. Always verify the base type, voltage, wattage, lumen output, beam angle, color temperature, dimming compatibility, fixture dimensions, and environmental rating before substituting a lamp.
What Does PAR Mean?
PAR stands for parabolic aluminized reflector. PAR lamps are designed to direct light forward in a controlled beam rather than distribute light evenly in all directions.
The number following PAR indicates approximate lamp diameter in eighths of an inch. For example, PAR30 means approximately 30/8 inch, or 3.75 inches, across.
This naming system is useful because it quickly tells you the approximate physical size of the lamp, but it does not specify the lamp’s lumen output, wattage, beam angle, color temperature, or electrical requirements.
PAR20 vs PAR30
The biggest difference between PAR20 and PAR30 is physical size.
A PAR20 is approximately 2.5 inches in diameter, while a PAR30 is approximately 3.75 inches. Because the PAR30 has a larger reflector and face, it is commonly used where more light output or a larger beam pattern is needed.
PAR20 lamps are often a better fit for:
- Smaller track-light heads
- Accent lighting
- Display lighting
- Smaller recessed fixtures
- Applications where a compact directional lamp is required
PAR30 lamps are often used for:
- Recessed downlights
- Larger track fixtures
- Retail lighting
- Display lighting
- Commercial interiors
- Higher-output accent lighting
Do not replace a PAR20 with a PAR30 simply because both use an E26 screw base. The larger PAR30 may not physically fit the fixture or may project beyond the trim.
PAR30 vs PAR38
A PAR38 is significantly larger than a PAR30.
The nominal diameter increases from approximately 3.75 inches for PAR30 to 4.75 inches for PAR38. PAR38 lamps are commonly selected when the fixture is designed for a larger lamp or when higher output and broader application capability are needed.
PAR38 lamps are frequently found in:
- Larger recessed fixtures
- Commercial floodlighting
- Exterior lighting
- Security lighting
- Retail spaces
- High-ceiling applications
- Indoor or outdoor directional fixtures when the specific lamp is rated for the environment
A PAR38 is not automatically a direct replacement for a PAR30. Even if the base and voltage match, check the fixture clearance, lamp length, lumen level, beam angle, and maximum permitted wattage.
PAR20 vs PAR38
PAR20 and PAR38 are at opposite ends of this common PAR-size range.
A PAR20 is about 2.5 inches in diameter, while a PAR38 is roughly 4.75 inches. The PAR38 therefore requires a substantially larger fixture opening and is generally used for applications requiring a larger optical system or greater output.
If you are choosing between these sizes, start with the fixture itself. A fixture designed for PAR20 normally should not be assumed to accommodate a PAR38, and vice versa.
PAR30 Long Neck vs Standard PAR30
PAR30 lamps may also be available in standard or long-neck configurations.
Both versions have approximately the same diameter, but their overall length differs. A long-neck PAR30 is designed for fixtures where the lamp needs to sit farther forward in the housing.
Manufacturer data shows that PAR30 and PAR30 long-neck versions can share similar diameters while having meaningfully different overall lengths.
When replacing an existing PAR30, check not only the “PAR30” designation but also the overall lamp length and neck style.
Beam Angle Matters as Much as Bulb Size
Two PAR lamps of the same physical size can produce very different lighting results.
A narrow beam concentrates light on a smaller area and is useful for accenting merchandise, artwork, architectural features, or work areas. A wider flood beam spreads light across a larger area.
When replacing a PAR lamp, try to match the original beam angle or beam designation whenever possible.
A replacement that physically fits but has the wrong beam angle can create:
- Dark areas
- Excessive glare
- Uneven lighting
- Poor accent definition
- Too much or too little light on the target
Lumen Output and Wattage Are Not the Same Thing
With LED lamps, wattage indicates electrical consumption, not light output.
When replacing an older halogen, incandescent, or HID-style lamp with LED, compare lumens, not just watts.
For example, two LED PAR38 lamps may consume similar wattage while producing different lumen output depending on efficiency, optics, and design.
For replacement work, verify:
- Required lumen output
- Existing lamp type
- LED replacement wattage
- Fixture maximum wattage
- Beam angle
- Color temperature
- Dimming compatibility
Color Temperature
PAR lamps are available in multiple color temperatures, commonly including warm white, neutral white, and cooler white options.
Changing color temperature can noticeably change how a space looks even if the lumen output stays the same.
For multi-lamp spaces, it is usually best to match the existing color temperature unless you are intentionally relamping the entire area.
Dimming Compatibility
Not every LED PAR lamp works with every dimmer.
Before installing an LED replacement in a dimmed circuit, confirm:
- The lamp is rated as dimmable
- The dimmer is compatible with LED loads
- The minimum load requirements are met
- The lamp manufacturer does not list restrictions for the intended control
An incompatible lamp/dimmer combination can cause flicker, poor low-end dimming, buzzing, or failure to shut off cleanly.
Indoor vs Outdoor Use
Do not assume every LED PAR lamp is suitable for outdoor use.
Some PAR lamps are rated for damp or wet locations, while others are intended for indoor use only. Check the manufacturer’s environmental rating before using the lamp in exterior, exposed, refrigerated, or other unusual conditions.
Industry guidance also notes that LED PAR lamps are not universally weatherproof, so the actual product listing and rating should be verified before outdoor installation.
PAR Replacement Checklist
Before replacing a PAR20, PAR30, or PAR38 lamp, verify:
- PAR size
- Physical diameter
- Overall lamp length
- Base type
- Voltage
- Wattage
- Lumen output
- Beam angle
- Color temperature
- CRI if important to the application
- Dimming compatibility
- Fixture clearance
- Indoor, damp, or wet-location rating
- Any application-specific requirements
Frequently Asked Questions
Can I replace a PAR30 with a PAR38?
Only if the fixture is designed to accommodate the larger PAR38 and the electrical and lighting specifications are compatible. A PAR38 is about one inch larger in diameter than a PAR30, so physical clearance is often the limiting factor.
Can I replace a PAR20 with a PAR30?
Sometimes, but not automatically. PAR30 is significantly larger than PAR20. Check fixture dimensions, base type, lamp length, wattage, lumens, and beam angle before substituting.
What is the difference between PAR20 and PAR30?
PAR20 is approximately 2.5 inches in diameter, while PAR30 is approximately 3.75 inches. PAR30 is physically larger and is commonly used in larger fixtures or applications requiring more output.
What is the difference between PAR30 and PAR38?
PAR30 is approximately 3.75 inches in diameter, while PAR38 is approximately 4.75 inches. PAR38 is larger and commonly used in higher-output indoor or outdoor directional applications.
Is PAR38 brighter than PAR30?
Not necessarily. PAR38 lamps often support higher output, but brightness depends on the specific lamp’s lumen rating, not just its physical size.
Do PAR20, PAR30, and PAR38 use the same base?
Many versions use an E26 medium screw base, but that should never be assumed. Verify the base listed on the existing lamp and the replacement lamp.
How do I know which PAR bulb I have?
Look for the lamp designation printed on the bulb or packaging. If that is unavailable, measure the bulb’s widest diameter. The PAR number corresponds approximately to diameter in eighths of an inch.
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