Last fall, I got a call that could have gone very wrong.
Our company—about 400 employees across three locations—was finally updating the lighting in our main office. The old 2x4 troffers with buzzing ballasts had been a running joke for years. But this wasn't just a cosmetic upgrade. Our facilities manager had retired, and the task landed on my desk.
I manage all our service ordering—roughly $350,000 annually across 8 vendors. But lighting? That was a new one. I knew we needed recessed LED fixtures, but the biggest question staring at me was: 4-inch vs 6-inch?
I went back and forth for almost two weeks. On paper, 6-inch cans seemed like the obvious choice—more light, bigger coverage area, industry standard. But my gut said something was off. Turns out, my gut was right.
“Never expected the smaller fixture to outperform the larger one. Turns out, spec sheets don't tell you everything.”
Background: The Project
We were retrofitting 12,000 square feet of open-plan office space plus 8 private offices and 3 conference rooms. The goal was simple: get rid of the troffers, install clean recessed lighting, and make the space feel less like a 1990s call center.
My budget was tight—not shoestring, but not unlimited. I had to cover fixtures, installation, and controls. And here's the kicker: we wanted to use Lithonia Lighting fixtures because the maintenance team already knew the brand from a warehouse retrofit two years earlier (that was a different story—I'll save it).
I reached out to my regular electrical supply vendor and asked for quotes on two configurations: 4-inch fixtures in more positions, versus 6-inch fixtures in fewer positions. Both options used Lithonia products—primarily the FML4W series for the 4-inch and certain BLWP4 models for utility spaces.
That's when the real education began.
The 4-Inch vs 6-Inch Comparison
What the Numbers Say
The conventional wisdom in commercial lighting is: bigger = better. More surface area, more lumens, fewer fixtures needed. That's true—to some extent.
A typical 6-inch LED recessed downlight produces around 1000-1200 lumens at about 90-100 lumens per watt. A 4-inch fixture? About 700-900 lumens at similar efficiency. So yes, 6-inch options give you more raw light output per fixture.
But this gets into lighting design territory, which isn't my expertise. I'm not an architect or a lighting designer. What I can tell you from a procurement perspective is this: raw output is only one variable.
What I Actually Discovered
My vendor, who I've worked with since 2020, gave me a spreadsheet comparing both options for our space. The difference that jumped out wasn't power consumption or even cost—it was layout flexibility and visual comfort.
Here's the oversimplified version of what I learned:
- 6-inch fixtures in our open-plan area needed to be spaced about 6-8 feet apart to get even coverage. That meant fewer cuts in the ceiling grid and lower installation costs. But they created hotspots—bright cones directly under each fixture with noticeable falloff between them. In a workspace, that's not ideal.
- 4-inch fixtures could be spaced tighter—about 3-5 feet apart. More fixtures, yes. But the light distribution was smoother. No hotspots. No dark zones between desks. The open plan felt more even and less like a surgical suite.
I spent one evening—seriously, like 10 PM on a Tuesday—walking through the office with a flashlight and a tape measure, sketching layouts on graph paper. My dog was confused. My wife thought I'd lost it.
The surprise wasn't the price difference—it was how much the beam angle changed everything. Many 6-inch fixtures have a wider beam spread (up to 120 degrees), but that can mean more glare at typical ceiling heights. The 4-inch fixtures (we looked at Lithonia's FML4W series) had a tighter beam—around 60-90 degrees—which actually worked better for task lighting above desks.
“The 4-inch vs 6-inch decision kept me up at night. On paper, 6-inch made sense. But my gut said the smaller fixtures would provide better task illumination. I was half right.”
To be fair, 6-inch fixtures have their place. Conference rooms with higher ceilings? 6-inch all day. But for standard office ceilings (about 9 feet), 4-inch was the better choice for task-oriented spaces.
The Decision Process
I'm pretty good at vendor consolidation. When I took over purchasing in 2020, we had 18 vendors. Now we're down to 8. But lighting was a new category for me, and I needed to make a call that wouldn't make me look bad to my VP when the project came in over budget or users complained about glare.
I went with a hybrid approach:
- Open office area: 4-inch Lithonia FML4W LED fixtures on a 4-foot grid. About 180 fixtures total for 12,000 square feet. The FML4W gave us good color rendering (CRI 90+) and dimmable drivers for future controls integration.
- Conference rooms: 6-inch fixtures (Lithonia's DSX series) for the higher ceilings and better ambient light distribution.
- Utility spaces (break rooms, storage, corridors): I used BLWP4 wall packs for exterior utility lights, and a mix of downlights for corridors.
Did I spec the chandelier mount for our conference room? Yes—but that was a separate project. The client (my COO) wanted a statement piece. I had to coordinate with an electrical contractor to install a proper chandelier mount junction box in the center of the room. That part was easy compared to the recessed lighting decision.
The Results
The installation took three weeks. We had to move people around (always fun), but the contractor we used—a mid-size outfit with 12 electricians—said the hybrid 4-and-6 approach was actually easier to install than a uniform 6-inch layout.
Why? Because the 4-inch fixtures weigh less. The FML4W series is about 2.5 pounds per fixture versus 5-7 pounds for a 6-inch trim. That matters when you're installing 180 of them.
Post-installation feedback from the team? Mostly positive. About 10% of staff in the open plan said the light felt odd at first—probably adjusting from the old troffers. After two weeks, nobody noticed. Which is exactly what you want: lighting that works so well, nobody thinks about it.
Energy savings tracked at about 55% compared to the old T8 troffers (we had submeters, so I can verify this). Payback period: roughly 3.2 years based on our utility rates (circa 2024).
What I'd Tell Someone Doing This for the First Time
If you're an office manager or admin buyer trying to navigate a lighting retrofit for the first time, here's my honest take:
- Don't assume bigger is better. 4-inch fixtures have advantages for task-lit spaces. They reduce glare and create more even distribution.
- Verify your ceiling height. If it's under 10 feet, seriously consider 4-inch. Over 10 feet, 6-inch or even 8-inch might be needed.
- Check the beam angle spec. A 4-inch Lithonia FML4W at 60-90 degrees will perform differently than a 6-inch at 120 degrees. Get the spec sheet.
- Budget for more fixtures with 4-inch. You save money on per-fixture cost (generally $15-30 less per fixture for 4-inch vs equivalent 6-inch), but you'll need more of them, plus more wiring and ceiling cuts.
- Consider future controls. Some Litonia fixtures come with Zigbee-ready drivers. If you might add occupancy sensors or daylight harvesting later, check compatibility now. Retrofitting controls is expensive.
I'm not a lighting designer—far from it. But managing this project taught me that the 4-inch vs 6-inch decision isn't a one-size-fits-all answer. It's about the specific use case, ceiling height, and how your team uses the space.
Would I do it differently? Maybe I'd have tested a mockup before committing to 180 fixtures. But given the timeline (our COO wanted it done before the end-of-year), we did the best we could with the information we had. And it worked out.
The vendor who treated my $350,000 total project seriously? Same vendor who helped me when my orders were $200. That relationship—built on trust, not transaction—made the whole thing possible.