What Is the Difference Between PAR20 and PAR38 Bulbs?

The Short Version

• Physical size: A PAR20 bulb measures 2.5 inches across the face, while a PAR38 bulb measures 4.75 inches across. A PAR38 is nearly twice as wide and noticeably heavier.
• Light output: A PAR20 bulb produces around 450 to 480 lumens for accent lighting and small spaces. A PAR38 bulb produces 1,050 to over 3,000 lumens to cast broad light over backyards, driveways, and high-ceiling rooms.
• Shared screw base: Both bulbs share the exact same E26 base, which is the standard medium screw base found in common household lamps and ceiling fixtures. Even though their screw threads are identical, their glass housings are completely different sizes.
• Best locations: PAR20 bulbs belong in compact 4-inch recessed ceiling cans, track lights, and kitchen range hoods. PAR38 bulbs belong in exterior security floodlights, landscape fixtures, and large 6-inch ceiling cans.

Quick Comparison: Diameter, Brightness, and Practical Uses

Holding both bulbs side by side makes the physical difference obvious right away. A PAR20 bulb is roughly the size of a small lemon. Its face measures about 2.5 inches wide, and the entire bulb stands roughly 3 inches tall. It feels light in the hand and fits neatly inside tight fixtures. In contrast, a PAR38 bulb is roughly the size of a large grapefruit. Its face measures nearly 5 inches wide, and its total length reaches around 5 inches. It has thick, heavy glass designed to shield the internal parts from harsh weather and heat.

Brightness is the second major dividing line. In lighting, brightness is measured in lumens, while wattage tells you how much electrical power the bulb consumes. A PAR20 bulb usually operates as a focused accent light. In LED versions, it draws around 7 watts to deliver roughly 450 to 470 lumens of brightness, which matches the light of an older 50-watt halogen bulb. Halogen PAR20 models draw around 39 to 50 watts to produce 480 lumens. This moderate brightness works well when you want to highlight a kitchen counter or illuminate a painting without washing out the entire room.

A PAR38 bulb operates as a heavy-duty workhorse designed to cover large areas. An LED PAR38 draws around 13 watts to pump out 1,050 lumens, which easily replaces an old 100-watt incandescent floodlight. Heavy-duty halogen PAR38 bulbs draw around 38 watts to produce up to 3,300 lumens of intense illumination. Putting a PAR38 bulb in a small bedroom fixture would create blinding glare, but that strong output is exactly what you need when you want to light up a dark driveway or monitor a wide backyard at night.

Their beam spread also creates different visual results. Beam spread describes the width of the pool of light cast onto a surface. A PAR20 casts a relatively tight, clean circle of illumination. It keeps light directed exactly where you point the fixture. A PAR38 throws a broad cone of light across tens of feet of yard, patio concrete, or high living room floors.

Decoding the Label: What PAR Numbers Mean in Inches

The letters and numbers stamped on lighting boxes look like confusing factory codes, but they follow a simple system. The letters "PAR" stand for parabolic aluminized reflector. In everyday language, a PAR bulb is a directional bulb with a flat face and a mirrored bowl inside. That mirrored bowl bounces light forward into a controlled beam instead of scattering light in every direction like a standard household teardrop bulb.

The number following the letters tells you the exact physical width across the widest part of the bulb face. In the United States, directional lighting manufacturers measure bulb diameters in eighths of an inch. Once you know that rule, you can figure out the size of any PAR bulb in seconds with basic math.

To find the diameter of a PAR20 bulb, take the number 20 and divide it by 8. Twenty eighths of an inch equals 2.5 inches (or 2 1/2 inches). When you lay a ruler straight across the glass lens of a PAR20 bulb, it measures exactly 2.5 inches from edge to edge.

To find the diameter of a PAR38 bulb, take the number 38 and divide it by 8. Thirty-eight eighths of an inch equals 4.75 inches (or 4 3/4 inches). The face of a PAR38 bulb is almost two and a quarter inches wider than a PAR20 bulb. Remembering the eighths-of-an-inch rule ensures you never have to guess whether a bulb will look right in your ceiling.

The Socket Trap: Why the Screw Base Fits Even When the Bulb Housing Fails

The biggest point of confusion for homeowners is that both of these bulbs use the exact same screw base. Both PAR20 and PAR38 bulbs feature an E26 base. This is the standard medium screw base used across North America in common table lamps, porch lights, and ceiling cans. Because the metal threads match, a PAR20 bulb will screw smoothly into a PAR38 socket, and a PAR38 bulb will screw into a PAR20 socket if there is nothing blocking the way.

This shared socket size creates an easy trap. Just because a bulb screws in does not mean it belongs in that fixture. If you screw a small PAR20 bulb into a large outdoor security shroud built for a PAR38, the bulb will turn on, but it will look and perform terribly. The small bulb sits buried deep inside the cavernous fixture housing. Most of the light rays bounce around inside the metal shroud instead of reaching your yard, leaving dark spots where you need safety lighting. In addition, an indoor-rated PAR20 bulb lacks the weather seals needed to keep wind-blown rain out of the electrical socket.

Trying the reverse creates physical damage. If you try to screw a large PAR38 bulb into a compact 4-inch ceiling can or a track lighting head, the broad glass face will slam against the metal trim before the brass threads even touch the socket. Forcing the bulb into the opening can crack the glass face, bend the ceiling trim, or damage the internal socket bracket.

Heat and electrical limits also matter. Before swapping bulbs, always check the safety sticker inside the fixture housing to verify the maximum allowed wattage. Older halogen bulbs generate extreme heat that can damage ceiling wiring if you exceed fixture ratings. If you are taking down an old, hot bulb to check its base, follow the safe way to change a halogen light bulb by cutting power at the wall switch and allowing the housing to cool completely before touching it with bare hands.

Where Each Bulb Belongs: Indoor Spots Versus Outdoor Floods

Choosing between these two sizes comes down to the fixture style, the ceiling height, and whether the bulb faces moisture. Here is a clear breakdown of where each option belongs in a home.

A PAR20 bulb works best in these locations:

• Compact 4-inch recessed ceiling cans: Modern kitchens, hallways, and bathrooms often use narrow 4-inch metal fixtures set into the ceiling. A PAR20 sits flush with the trim ring, delivering a tidy, professional look.
• Track lighting heads: When you want focused task lighting over an island or display, focused spot light bulbs for indoor tracks in a PAR20 size keep the track heads looking sleek rather than bulky.
• Kitchen range hoods: Many stove ventilation hoods feature small recessed sockets pointing straight down at the cooktop. Compact PAR20 bulbs fit inside these protective cutouts without hanging down into your cooking space.
• Accent and art displays: Because a PAR20 casts a controlled beam, it works well in directional eyeball ceiling fixtures aimed at framed artwork, textured stone fireplaces, or decorative shelving.

A PAR38 bulb works best in these locations:

• Exterior security floodlights: Dual-socket motion lights mounted on garage corners, back doors, and barn gables are specifically shaped to hold the wide bell of a PAR38.
• Large 6-inch recessed ceiling cans: Older homes and commercial spaces frequently feature wide 6-inch cans. A PAR38 fills the wide ceiling opening completely, preventing an empty, cavernous gap around the bulb.
• High or vaulted ceilings: In two-story living rooms or cathedral entryways where ceilings rise 12 to 20 feet high, a smaller bulb will leave the room dim. The intense lumen output of a PAR38 pushes light all the way down to the living space.
• Landscape up-lighting: Outdoor ground fixtures aimed up into mature oak trees or against wide exterior brick walls need the heavy throw and wide face of a PAR38 to illuminate large outdoor surfaces.

Always pay close attention to damp and wet location ratings on the package. A damp-rated bulb is built to handle humidity and condensation, making it suitable for covered porches or bathroom ceilings above a shower. A wet-rated bulb features weather seals that resist direct rainfall, melting snow, and garden sprinklers. Exterior floodlights must always use wet-rated bulbs to prevent water from penetrating the electrical socket.

How to Measure Your Fixture Opening Before Ordering

If you are standing in a room looking up at an empty socket, you do not have to guess which bulb size to order. Measuring your fixture takes less than two minutes and prevents the frustration of returning the wrong product.

1. Switch off the power: Turn off the wall switch that controls the fixture. If the light was recently on, wait ten minutes for the metal housing to cool down completely so you do not burn your fingers.
2. Measure the inner opening diameter: Grab a rigid tape measure or a simple wooden ruler. Place the tip against the inner metal lip of the fixture opening and measure straight across the center to the opposite inner lip. Measure only the open hole, not the decorative plastic or metal trim ring resting flat against your drywall ceiling.
3. Match your measurement to the bulb size:
   • If the opening measures between 3.25 inches and 4 inches across, your fixture requires a compact bulb like a PAR20.
   • If the opening measures between 5 inches and 6.5 inches across, your fixture is built for a wide reflector like a PAR38.
4. Check internal depth and clearance: Measure from the base of the screw socket straight out to the ceiling surface. Shallow ceiling cans cannot accommodate long-necked bulbs. A standard PAR20 needs roughly 3 inches of clearance, while a PAR38 requires at least 5 inches of depth inside the housing so the glass does not stick out past the trim.
5. Read the manufacturer sticker: Look closely inside the metal housing with a flashlight. Every certified fixture has a white or silver label stamped inside the metal can. This sticker clearly states the approved bulb shapes (such as PAR20, BR30, or PAR38) and the maximum safe wattage allowed by the manufacturer.

What to Look for When Choosing Your Replacement Bulb

Once you confirm whether your fixture requires a PAR20 or a PAR38, picking the right replacement comes down to four basic features printed on the retail package.

First, verify the lighting technology. While traditional halogen bulbs provide immediate heat and smooth dimming, modern LED versions use up to 80 percent less electrical power while lasting thousands of hours longer. Choosing an LED replacement also keeps ceiling cans cooler, protecting older wiring in your attic.

Second, shop by lumens instead of watts. If you need a gentle accent beam for an indoor spotlight, look for a PAR20 bulb offering roughly 450 to 500 lumens. If you are replacing an outdoor security floodlight, choose a PAR38 bulb that delivers at least 1,000 to 1,500 lumens so you get full visibility across your yard.

Third, match the color temperature to your room ambiance. Color temperature is measured in Kelvin (K). A 2700K bulb delivers soft warm white light with a cozy, amber tone that looks great in bedrooms and living rooms. A 3000K bulb provides crisp, clean warm white light that flatters bathroom mirrors and kitchen counters. For outdoor security fixtures, many homeowners prefer 4000K natural white or 5000K daylight white, which casts a bright, clean light that makes it easy to spot nighttime movement.

Finally, check your wall control compatibility and weather ratings. If your fixture connects to a dimmer switch, make sure the bulb package clearly states that it is dimmable. Non-dimmable LED bulbs placed on dimmer circuits will buzz, flicker, or burn out prematurely. For any exterior fixture exposed to rain, confirm that the bulb is explicitly marked as wet-rated before screwing it in.

1

Feit Electric PAR20 LED Light Bulb, 50W Equivalent, Dimmable, Color

View on Amazon

• LFR Score

  LFR Score is a ranking system developed by lightfansreviews.com. LFR Score has no relationship or impact from any manufacturers or sales agent websites. Learn more

  9.4
• Brand
  Feit Electric

Key specs2

Color Temperature Flexibility

5 selectable CCT options

Moisture Protection

Damp rated for bathrooms

Pros & cons43

Pros

• Five selectable color temperatures provide adaptable lighting across different indoor rooms
• High 90 CRI helps reveal true, vibrant surface colors
• Damp rating permits installation in moisture-prone areas like bathrooms
• Consumes less energy while delivering 450 lumens to replace a standard 50-watt bulb

Cons

• Requires manual switch adjustment on each bulb to change color temperature
• Spotlight beam profile focuses light narrowly rather than dispersing broad ambient coverage
• Pack contains only two bulbs, requiring multiple purchases for larger multi-can rooms

2

Vinaco PAR20 Flood Light Bulb, 6 Pack PAR20 Flood 39W

View on Amazon

• LFR Score

  LFR Score is a ranking system developed by lightfansreviews.com. LFR Score has no relationship or impact from any manufacturers or sales agent websites. Learn more

  9.2
• Brand
  Vinaco

Key specs2

Color Rendering Fidelity

100 CRI with 2800K warm white

Recessed Can Compatibility

Measures 2.48 inches wide to fit snugly inside standard 4-inch indoor recessed ceiling cans, track heads, and range hood sockets.

Pros & cons43

Pros

• Full 100 CRI halogen output delivers natural, true-to-life color rendering
• Smooth dimming range from 10 percent to 100 percent without warm-up delay
• Generates 480 lumens instantly for track heads and small 4-inch ceiling cans
• Clear glass envelope fits standard range hoods and recessed fixtures

Cons

• Consumes 39 watts of actual power, generating more heat than LED alternatives
• Rated 3000-hour lifespan requires significantly more frequent replacement than LED options
• Halogen filament remains sensitive to physical vibration in high-movement fixtures

3

Sunco 6 Pack Outdoor Flood Light Bulb LED PAR38, Exterior

View on Amazon

• LFR Score

  LFR Score is a ranking system developed by lightfansreviews.com. LFR Score has no relationship or impact from any manufacturers or sales agent websites. Learn more

  9.2
• Brand
  Sunco Lighting

Key specs2

Weather Resistance

UL wet rated and weatherproof

Outdoor Security Lighting

Produces 1050 lumens at 13 watts, delivering wide exterior floodlight coverage for driveways, yards, and open architectural eaves.

Pros & cons42

Pros

• High 1050 lumen output projects bright security illumination across outdoor yards
• Wet rating and weatherproof housing withstand direct rain and outdoor exposure
• Efficient 13-watt LED design delivers the light output of a traditional 100-watt bulb
• UL listing confirms compliance with established electrical safety standards

Cons

• Large PAR38 profile is physically too wide for compact 4-inch indoor ceiling cans
• Fixed 3000K warm white tone cannot be adjusted to cooler white shades

4

Ivyemons PAR20 Flood 39W 120V 480 Lumens- 6 Pack PAR20

View on Amazon

• LFR Score

  LFR Score is a ranking system developed by lightfansreviews.com. LFR Score has no relationship or impact from any manufacturers or sales agent websites. Learn more

  9.2
• Brand
  Ivyemons

Key specs2

Fixture Enclosure Fit

2.36-inch diameter for 4-inch cans

Incandescent Replacement

Replaces traditional incandescent R20 bulbs directly using an E26 screw base, providing 480 lumens of 2800K warm light.

Pros & cons42

Pros

• Direct screw-in replacement for older incandescent R20 and PAR20 bulbs
• Smooth dimming from 10 percent to 100 percent without noticeable flicker
• Compact 2.36-inch width fits cleanly into tight range hoods and 4-inch recessed cans
• Certified under CE and RoHS safety and environmental standards

Cons

• Draws 39 watts of line power, creating notable heat in enclosed fixtures
• Rated for 3000 hours, requiring earlier maintenance compared to solid-state LEDs

5

BOGAO Par20 Bulbs, 2 Pcs 120V 50W Par20 Light Bulbs,

View on Amazon

• LFR Score

  LFR Score is a ranking system developed by lightfansreviews.com. LFR Score has no relationship or impact from any manufacturers or sales agent websites. Learn more

  9.0
• Brand
  BOGAO

Key specs2

Range Hood Suitability

Designed with an E26 medium base and reflector flood housing to fit overhead range hoods needing focused downward warmth.

Operating Voltage

Standard 120V line voltage

Pros & cons33

Pros

• Standard E26 medium screw base threads easily into standard domestic sockets
• Reflector flood design focuses beam downward for targeted range hood cooking illumination
• Delivers high-output 50-watt warm incandescent light for cozy indoor spaces

Cons

• Listing does not state rated lifespan hours, requiring buyer verification
• Draws a full 50 watts per bulb, producing considerable operating heat
• Lumen rating is omitted from specifications, leaving exact brightness unstated

6

Sunco 10 Pack PAR20 LED Bulbs 50W Equivalent 7W Dimmable,

View on Amazon

• LFR Score

  LFR Score is a ranking system developed by lightfansreviews.com. LFR Score has no relationship or impact from any manufacturers or sales agent websites. Learn more

  9.0
• Brand
  Sunco Lighting

Key specs2

Ingress Protection

IP65 waterproof and UL listed

Energy Consumption

7 watts replaces 50-watt halogen

Pros & cons42

Pros

• IP65 waterproof rating protects internal circuitry during outdoor soffit and damp indoor use
• Draws only 7 watts while matching 50-watt traditional floodlight output
• High 90 CRI rating ensures accurate, vibrant color presentation indoors
• Backed by UL safety listing and packaged in a generous 10-bulb pack

Cons

• Generates 470 lumens, which is insufficient for broad outdoor security yard coverage
• Fixed 3000K warm white tone lacks cooler temperature adjustments

7

Ivyemons PAR20 Flood 39W 120V 480 Lumens- 2 Pack PAR20

View on Amazon

• LFR Score

  LFR Score is a ranking system developed by lightfansreviews.com. LFR Score has no relationship or impact from any manufacturers or sales agent websites. Learn more

  9.0
• Brand
  Ivyemons

Key specs2

Pack Size Utility

2-pack for targeted single-room updates

Dimming Control Range

10% to 100% smooth adjustment

Pros & cons42

Pros

• Two-pack bundle suits single fixtures or dual range hood socket replacements
• Smooth dimming from 10 percent to 100 percent allows easy mood lighting control
• Compact 2.36-inch diameter threads smoothly into cramped track fixtures
• Provides instant 480-lumen warmth with no initial ignition delay

Cons

• Tungsten filament generates surface heat requiring careful fixture clearance
• Limited 3000-hour operational life compared to standard LED longevity

8

Amazon Basics 50W Equivalent, 3000K White, Dimmable, 10,000 Hour Lifetime,

View on Amazon

• LFR Score

  LFR Score is a ranking system developed by lightfansreviews.com. LFR Score has no relationship or impact from any manufacturers or sales agent websites. Learn more

  8.8
• Brand
  Amazon Basics

Key specs2

Rated Operating Life

10,000 hours of LED operation

Track Lighting Application

PAR20 profile and dimmable capability make these bulbs suitable for indoor multi-head track lights and living room accent fixtures.

Pros & cons42

Pros

• Solid 10,000-hour rated operating life significantly lowers maintenance frequency
• Provides dimmable illumination to easily adjust light levels in living spaces
• LED efficiency matches 50-watt traditional output with lower power consumption
• Six-bulb pack provides enough units to re-lamp an entire track run

Cons

• Lumen output and wattage draw are unstated in the listing and must be verified
• Wet location rating is not specified, limiting safe use to indoor dry fixtures

9

KIMLOONG PAR20 Halogen Light Bulbs, 39W 120V Dimmable 6 Pack,

View on Amazon

• LFR Score

  LFR Score is a ranking system developed by lightfansreviews.com. LFR Score has no relationship or impact from any manufacturers or sales agent websites. Learn more

  8.8
• Brand
  KIMLOONG

Key specs2

Luminous Output

1755 lumens from a compact PAR20

Light Quality & Tone

2700K warm white with 100 CRI

Pros & cons42

Pros

• Listed 1755 lumen output delivers exceptional halogen illumination for its compact frame
• Full 100 CRI rating reproduces vivid, natural indoor color tones
• Cozy 2700K warm white glow creates a welcoming atmosphere in retail or home settings
• Continuous dimming down to 10 percent without operational hum or delay

Cons

• Draws 39 watts per bulb, producing substantial heat during extended use
• High lumen halogen output may generate glare in low ceiling installations

10

Rnyloas PAR38 Halogen Flood Light Bulbs Dimmable, 38W 120V Par38

View on Amazon

• LFR Score

  LFR Score is a ranking system developed by lightfansreviews.com. LFR Score has no relationship or impact from any manufacturers or sales agent websites. Learn more

  8.2
• Brand
  Rnyloas

Key specs2

Maximum Brightness

3300 lumens for heavy flood coverage

Large Fixture Requirement

Wide PAR38 housing is engineered for large outdoor flood mounts or deep commercial cans, making it too wide for residential 4-inch recessed trims.

Pros & cons43

Pros

• Produces an intense 3300 lumens for maximum outdoor flood and large room coverage
• CRI 100 rating ensures authentic daylight-grade color accuracy
• Smooth 10 percent to 100 percent dimming allows fine light level adjustment
• Standard E26 base fits large open outdoor fixtures and deep commercial cans

Cons

• Large PAR38 profile will not fit inside compact 4-inch or 5-inch ceiling cans
• Rated 2000-hour lifespan is the shortest among compared models
• Substantial light output may overpower small indoor living areas

Last update on 2026-10-01 / Affiliate links / Images, Product Titles, and Product Highlights from Amazon Product Advertising API

FAQs

Can I screw a PAR20 into a fixture designed for a PAR38?

Yes, the bulb will screw into the socket because both bulbs share the standard E26 medium screw base. But doing this causes poor performance and looks strange. The tiny bulb will sit buried deep inside the wide fixture housing, trapping the light beam inside the metal can and failing to illuminate the surrounding space properly.

Can PAR38 bulbs be used inside the house?

PAR38 bulbs can be used indoors, but only inside fixtures specifically designed for their large size, such as deep 6-inch recessed ceiling cans. They are popular in rooms with tall cathedral or vaulted ceilings where light needs to travel a long distance to reach the floor. Using them in standard eight-foot ceilings often creates uncomfortably bright glare.

Are PAR20 and PAR38 bulbs dimmable?

Halogen versions of both bulbs dim smoothly on standard wall switches. If you buy modern LED bulbs, you must check the retail box to verify they are labeled as dimmable. Installing a non-dimmable LED bulb on a dimmer switch will lead to rapid buzzing, annoying strobe-like flickering, and early electronic failure.

Why do outdoor floodlights require wet-rated bulbs instead of damp-rated ones?

Wet-rated bulbs feature watertight seals around the glass lens and internal electronics to prevent rain, blowing snow, and sprinkler water from reaching live electrical components. Damp-rated bulbs are only built to withstand airborne moisture and humidity, meaning direct rainwater hitting the glass can cause electrical shorts or socket corrosion.