LED Downlight Buying Guide: Sizes, Beam Angles & CRI Explained
What Is an LED Downlight?
An LED downlight is a recessed light fixture installed into a ceiling opening that casts a broad, downward beam of light. Also called a recessed downlight or can light, it consists of three main components: the LED light source (COB or SMD), the heat-dissipating housing, and the trim that sits flush with the ceiling surface. LED downlights are the most widely used fixture for general ambient lighting in commercial spaces because they provide uniform, low-glare illumination while maintaining a clean, minimalist ceiling aesthetic.
Unlike LED spotlights, which produce a narrow focused beam for accent lighting, downlights are designed to spread light evenly across a room. Unlike LED surface downlights, which mount on top of the ceiling, recessed downlights require a cutout hole and sufficient ceiling cavity space.
This guide explains every specification you need to know when buying LED downlights for commercial projects — from cutout sizes and beam angles to CRI, color temperature, dimming, and IP ratings.
Common LED Downlight Sizes & Cutout Dimensions
LED downlights are categorized by their cutout diameter — the hole you must drill into the ceiling. Choosing the right size depends on ceiling height, room size, and desired spacing.
| Cutout Size | Typical Outer Diameter | Common Power Range | Recommended Ceiling Height | Typical Application |
| 68–75 mm (2.5") | 80–90 mm | 3W–7W | 2.4–2.8 m | Corridors, small offices, hotel bathrooms |
| 90–100 mm (3") | 105–115 mm | 7W–12W | 2.6–3.0 m | General office, retail, hotel rooms |
| 120–130 mm (4") | 135–150 mm | 12W–20W | 2.8–3.5 m | Lobbies, showrooms, supermarkets, classrooms |
| 150–170 mm (5") | 175–190 mm | 20W–30W | 3.0–4.0 m | High-ceiling retail, conference rooms, atriums |
| 200–220 mm (6–8") | 220–260 mm | 30W–50W | 3.5–5.0 m | Airports, stadium concourses, warehouse offices |
Size Selection Rule of Thumb
- Ceiling height ≤ 2.8 m: Use 75mm or 90mm cutout downlights (3W–12W)
- Ceiling height 2.8–3.5 m: Use 120mm or 150mm cutout downlights (12W–30W)
- Ceiling height > 3.5 m: Use 170mm+ downlights or consider high-bay fixtures instead
Always confirm the ceiling cavity depth — most LED downlights need 50–120mm of space above the ceiling for the housing and driver.
Beam Angles Explained
The beam angle determines how widely the light spreads from the fixture. It is measured as the angle at which light intensity drops to 50% of the peak (the "half-peak" angle). Choosing the wrong beam angle leads to either dark spots between fixtures (too narrow) or wasted light spilling onto walls (too wide).
| Beam Angle | Classification | Best For | Spacing Guide |
| 15°–24° | Narrow | High ceilings, accent lighting, spotlight-like effects | Fixtures spaced close together |
| 36°–45° | Medium Narrow | General lighting in rooms with 2.6–3.0 m ceilings | 1.2–1.5 × ceiling height |
| 60° | Medium (Most Common) | Standard commercial general lighting | 1.5 × ceiling height |
| 90°–100° | Wide | Low ceilings (≤2.6 m), corridors, areas needing wide coverage | 1.5–2.0 × ceiling height |
| 120°+ | Extra Wide | Very low ceilings, cove lighting, wall-wash effects | Wide spacing possible |
How to Calculate Downlight Spacing
A common formula for uniform general lighting:
Spacing = Ceiling Height × 1.5 (for 60° beam angle)
For example, with a 3.0 m ceiling and 60° downlights, space fixtures approximately 4.5 m apart. Maintain at least 0.5–0.75 m from the first fixture to the wall to avoid dark edges.
Color Temperature Guide
Color temperature (measured in Kelvin, K) describes the warmth or coolness of white light. It significantly affects the mood and functionality of a commercial space.
| Color Temperature | Appearance | Best Commercial Applications |
| 2700K | Warm White (similar to incandescent) | Hotel rooms, restaurants, lounges, high-end retail |
| 3000K | Soft Warm White | Hotel lobbies, retail, residential-style commercial, healthcare |
| 4000K | Neutral White (Most Popular) | Offices, classrooms, hospitals, supermarkets, general commercial |
| 5000K | Cool White | Warehouses, industrial, laboratories, task lighting |
| 6500K | Daylight | Showrooms, jewelry stores, areas needing maximum color clarity |
Key Recommendation
For most commercial projects, 4000K neutral white is the safest default — it provides clear, comfortable illumination without the yellow tint of warm white or the harsh blue of cool white. For retail and hospitality, 3000K creates a more inviting atmosphere. Always use a single color temperature within one room to avoid visible mismatches.
CRI (Color Rendering Index) Explained
The Color Rendering Index (CRI or Ra) measures how accurately a light source reveals the true colors of objects compared to a reference light source (natural daylight or incandescent). CRI ranges from 0 to 100 — the higher the number, the more accurate the color rendering.
| CRI Value | Quality Level | Suitable Applications |
| CRI 70–79 | Basic | Warehouses, storage, industrial, low-budget projects |
| CRI 80–89 | Good (Standard Commercial) | Offices, corridors, classrooms, general retail |
| CRI 90–95 | Excellent | High-end retail, fashion stores, art galleries, museums, restaurants |
| CRI 95+ | Professional | Museums, galleries, jewelry, makeup studios, medical examination |
Why CRI Matters in Commercial Lighting
- Retail: A CRI 90+ light makes clothing, food, and products look more vibrant and true-to-life, directly influencing purchasing decisions.
- Offices: Adequate CRI (80+) reduces eye strain and improves visual comfort for long working hours.
- Art & Museums: CRI 95+ is essential to preserve the artist's intended color appearance.
- Healthcare: High CRI helps medical staff accurately assess skin tone and patient condition.
R9 Value — The Often-Overlooked Spec
CRI is an average of 8 color samples (R1–R8). R9 measures the rendering of saturated red — a separate, extended index. For retail, fashion, and food lighting, insist on R9 ≥ 50 (ideally ≥ 80). A light can have CRI 90 but a negative R9, making reds appear dull and brownish.
IP Ratings for LED Downlights
The Ingress Protection (IP) rating indicates a fixture's resistance to dust and water. For downlights, the IP rating determines where they can be safely installed.
| IP Rating | Protection Level | Suitable Locations |
| IP20 | Dust-protected, no water resistance | Dry indoor areas: offices, corridors, hotel rooms |
| IP44 | Splash-proof from all directions | Bathrooms (zone 2/3), kitchens, covered balconies |
| IP54 | Dust-protected + splash-proof | Industrial areas, outdoor covered areas, car parks |
| IP65 | Dust-tight + water jet resistant | Bathrooms (zone 1), outdoor soffits, wet areas |
For standard commercial indoor applications, IP20 is sufficient. For bathrooms, kitchens, and any area with moisture exposure, specify IP44 or higher.
Dimmable vs. Non-Dimmable LED Downlights
Dimmable Downlights
Dimmable LED downlights allow brightness adjustment, providing flexibility for different activities and moods. They require a compatible LED dimmer switch.
Advantages:
- Energy savings when dimmed
- Flexibility for multi-use spaces (e.g., conference rooms that switch between presentations and meetings)
- Mood control in hospitality and retail
- Extended LED lifespan (lower current = less heat)
Disadvantages:
- Higher upfront cost (dimmable drivers + dimmer switches)
- Requires compatible dimmers (standard TRIAC dimmers may cause flickering)
- Potential compatibility issues between driver and dimmer
Non-Dimmable Downlights
Non-dimmable downlights operate at full brightness at all times.
Advantages:
- Lower cost
- Simpler installation
- No compatibility issues
Disadvantages:
- No flexibility
- May waste energy in spaces that don't always need full brightness
Dimming Protocols
| Protocol | Best For | Features |
| TRIAC (Phase-Cut) | Retrofit, simple installations | Low cost, widely available, may flicker with cheap drivers |
| 0-10V | Commercial, offices | Reliable, smooth dimming, requires additional control wiring |
| DALI | Large commercial, smart buildings | Digital, addressable, individual fixture control, higher cost |
| Zigbee / Wi-Fi | Smart homes, small commercial | Wireless control, app/voice integration, may need gateway |
For commercial projects, 0-10V dimming is the most common and reliable choice. For smart buildings, DALI offers the most control flexibility.
How to Choose the Right LED Downlight: 8-Point Checklist
Use this checklist when specifying LED downlights for any commercial project:
- Determine the application — Is it general office lighting, retail display, hotel room, or corridor? This dictates all other specs.
- Measure ceiling height and cavity depth — Higher ceilings need larger/more powerful fixtures; shallow cavities may require low-profile or surface-mounted alternatives.
- Choose cutout size — Match to ceiling height and room size (see size table above).
- Select beam angle — 60° is standard for general lighting; narrower for high ceilings, wider for low ceilings.
- Pick color temperature — 4000K for general commercial, 3000K for hospitality/retail, 2700K for upscale dining.
- Specify CRI — Minimum CRI 80 for general use; CRI 90+ for retail, galleries, and food service. Check R9 ≥ 50.
- Confirm IP rating — IP20 for dry areas, IP44+ for bathrooms/kitchens, IP65 for wet/outdoor areas.
- Decide on dimming — Non-dimmable for simple spaces; 0-10V or DALI dimmable for commercial flexibility.
Frequently Asked Questions (FAQ)
Q: What is the difference between an LED downlight and an LED spotlight?
A: An LED downlight produces a wide beam (typically 60°–120°) for general ambient illumination, while an LED spotlight produces a narrow beam (15°–45°) to highlight specific objects or areas. Downlights are usually fixed in position, whereas spotlights are often adjustable (tilt and rotate). For a detailed comparison, read our guide on [LED downlight vs. spotlight vs. surface downlight differences](https://www.okelilamp.com/commercial-led-lighting-manufacturer-china-guide).
Q: How many LED downlights do I need per square meter?
A: As a general rule for standard office lighting (300–500 lux at desk level with 2.8m ceiling), you need approximately one 12W–15W downlight per 4–6 m², spaced 1.5–2.0 m apart. However, the exact number depends on fixture wattage, beam angle, ceiling height, required lux level, and reflectance of walls/ceiling. Always use lighting design software (DIALux or Relux) for precise calculations.
Q: Can LED downlights be covered with insulation?
A: Only IC-rated (Insulation Contact) downlights can be directly covered with thermal insulation. Non-IC-rated downlights require a minimum clearance (typically 50–100mm) from insulation to prevent overheating. Always check the manufacturer's specifications. For commercial projects with insulated ceilings, specify IC-rated fire-rated downlights.
Q: What is the lifespan of an LED downlight?
A: Quality LED downlights have a rated lifespan of 30,000–50,000 hours (L70 — the time until brightness drops to 70% of initial output). At 10 hours of daily use, 50,000 hours equals approximately 13.7 years. Lifespan depends on driver quality, thermal management, and operating environment. Always check the L70 rating and LM-80 test reports.
Q: Are LED downlights fire-rated?
A: Not all LED downlights are fire-rated. Fire-rated downlights are designed to maintain the fire resistance of a ceiling for a specified period (typically 30, 60, or 90 minutes). They are required in commercial buildings, multi-occupancy residential, and any ceiling that forms part of a fire compartment. Always specify fire-rated downlights where building regulations require them.
Q: What is the difference between COB and SMD LED downlights?
A: COB (Chip on Board) downlights use a single LED module with multiple chips packed together, producing a uniform, shadow-free light with excellent color consistency. They are preferred for high-end commercial and retail applications. SMD (Surface Mount Device) downlights use individual LED chips mounted on a PCB, offering higher energy efficiency and lower cost but potentially visible individual light points. COB generally provides better beam control and color consistency; SMD is more cost-effective for general lighting.
Conclusion
Choosing the right LED downlight involves balancing size, beam angle, color temperature, CRI, IP rating, and dimming capability. For most commercial projects, a 120mm cutout, 12W–15W, 60° beam, 4000K, CRI 80+, IP20 downlight is a reliable default. For retail and hospitality, upgrade to CRI 90+ with R9 ≥ 50 and 3000K color temperature. For wet areas, specify IP44 or higher.
Always request LM-79 photometric reports, LM-80 lifetime data, and IES files from your supplier before placing a bulk order. And whenever possible, evaluate physical samples for build quality, color consistency, and thermal performance.
About OKELI Lighting: With 16+ years of experience, OKELI manufactures a full range of commercial LED downlights — from 3W mini downlights to 50W high-power fixtures — with COB and SMD options, CRI up to 95+, dimmable drivers (0-10V, DALI, TRIAC), IP20 to IP65 ratings, and fire-rated models. All products undergo 48-hour aging tests and hold CE, RoHS, and ISO9001 certifications. For custom OEM/ODM downlight solutions, [contact OKELI Lighting](https://www.okelilamp.com/contact) for samples and quotations.
*Disclaimer: This guide is based on OKELI Lighting's manufacturing experience and industry standards. Specific project requirements may vary. Always consult a qualified lighting designer and local building codes before finalizing specifications.*
