I read through Jack Lindsey's article in the section on shop lighting, and ran through a bunch of calculations, and it has managed to completely confuse and annoy me. This is what I have, that I plugged into his simple formula:

800 sf shop (approx. 24 x36), 10' ceiling, walls and ceiling painted white. 100 foot-candles at work surface.

Assuming 40% of fixture lumens gets to work surface, 800 sf x 100 fc = 80,000 lumens required / 0.4 = 200,000 fixture lumens required.

I planned on using a Commercial Electric LED shop light from Home Depot (SKU 1000532467) which claims 3600 lumens. If I plug that into the formula, I get 56 (!) fixtures required. Fifty-six. No way. Even if I made a reasonable assumption that 60% of the usable lumens are reaching the work surface, I'm at 133,333 lumens which is still 37 fixtures. I can hang the lights a lot lower but that tends to ruin the purpose of the 10' ceilings.

What's wrong with this picture? Where are my assumptions or calculations way off here? I read on other forums about people allegedly lighting their huge pole barn shop with a half-dozen fixtures and being able to conduct neurosurgery, so what gives?