Selecting recessed lighting—often called "can lights" or "downlights"—is one of the most impactful decisions you will make for your home or project. This guide moves beyond the basics to provide the technical standards used by architects and lighting designers.
Step 1: The "Which One Do I Need?" Project Matcher
Before looking at sizes, identify your project type.
- New Construction? You need Housings (the metal frame installed before drywall).
- Replacing an old bulb/trim? You need Retrofit LED Kits (screws into existing cans).
- Tight ceiling space or remodeling? You need Canless Wafer Lights (clips directly to drywall).
- Sloped ceiling? You need Gimbal/Adjustable fixtures.
- Condo or Multi-Family? You likely need Fire-Rated fixtures.
Step 2: Understand the "Plenum" and Clearance
One of the most ignored technical details is Plenum Depth—the space between your ceiling and the floor or roof above it.
- Standard Cans: Require 5 to 7 inches of vertical clearance.
- Canless (Wafers): Require less than 2 inches. Using Ledvance technical data, we know these "panel style" lights fit within the thickness of standard 1/2" drywall, allowing you to install them even if a structural joist is in the way.
Step 3: Choosing Your Aperture (Size)
The size of the light (aperture) defines the "feel" of the room.
| Size | Best For | Note |
| 2 or 3-inch | High-end architectural accenting | "Pinhole" look; minimal ceiling clutter |
| 4-inch | Modern Residential Standard | Sleek, designer look; perfect for kitchens |
| 6-inch | General ambient lighting | Traditional standard; widest beam spread for large rooms |
Step 4: Decoding Lumens and Wattage (The Equivalency Chart)
Stop shopping by "Wattage." In 2026, Lumens are the only accurate measure of brightness. Use this Ledvance-standard chart to convert your old-school expectations:
| Old Incandescent | Modern Lumens | Best Room Type |
| 40W - 60W | 450 - 600 Lumens | Closets, Pantries, Hallways |
| 65W - 75W | 750 - 900 Lumens | Standard Bedrooms & Kitchens |
| 100W+ | 1200+ Lumens | High Ceilings (10ft+) & Lobbies |
Step 5: Select Your Color Temperature (Kelvin)
Color temperature (CCT) is measured in Kelvins. Many modern fixtures now come with Selectable CCT, but these are the industry standards:
- 3000K (Soft White): The designer's choice for a warm, residential feel.
- 4000K (Cool White): A clean, crisp white for kitchens, laundries, and offices.
- 5000K (Daylight): Best for high-task areas like garages or craft rooms.
Step 6: The Layout Standard (The Half-Height Rule)
Standardize your spacing with the Kichler Spacing Rule: Divide your ceiling height by two.
Height / 2 = Distance between lights. For a standard 8-foot ceiling, place your lights 4 feet apart. To avoid "hot spots" on walls, always place your first row 12 to 18 inches away from the wall.
Making Your Final Choice
Selecting the right recessed lighting is more than just picking a size; it’s about understanding the specific physical and functional needs of your space. By identifying your plenum depth, following the Half-Height spacing rule, and choosing the correct lumen output, you ensure your lighting is both beautiful and high-performing. Whether you opt for the architectural precision of 4-inch gimbals or the versatile ease of canless wafer lights, these technical standards will help you build a lighting system that lasts for years.
