Tools
Average footcandles and power density
The lumen method, the way it gets checked on a plan review. Give it the room, the fixture count and the delivered lumens, and it returns average maintained footcandles and watts per square foot.
Two numbers come out of the same three inputs. The first is the average light level the room will hold once the fixtures have aged and been cleaned a few times. The second is the lighting power density, which is what an energy plan reviewer looks at.
Use delivered lumens from the photometric file for the exact catalog number, including the optic, the finish and the driver setting. Nominal lumens from a family datasheet will flatter the answer, sometimes badly. If you tell me the catalog numbers I will pull the real delivered figures rather than the family averages.
Before you rely on it
This is arithmetic, not a photometric calculation. It will get you to a sensible starting point and tell you when something is obviously wrong, but a real layout gets run in AGi32 against the actual IES files. Send me the plan and I will run it properly.