Lmbo. Welcome to the world unknown where everyone has an opinion..
In the end, one has to look at the most limiting factor outside of your control. Canopy space..
You can be the best fucking grower in the world, you can't create extra space when non exists.
I used to convert watt per sq ft into grams and sometimes it worked and sometimes it didn't add up. With today's LEDs, it's all over the place. HpS you get a more stable conversion from watt 2 gram.
I don't try to calculate anything anymore. I just try to grow as best I can with the end mind of filling that canopy without over doing it.
There's is no wrong way. You can 20 or 1 plant. Take 3 months or 7 months. I harvest or 3 harvests. In the end, you get about the same yeild if you fill the canopy.
When a website says 400g yield, they calculate this based on area space. Why? Because there's only so much area you can fill up. So my bud has a 400g rating in a 4x4. That means technically, 400 watts out the wall in a 4x4 will give me max yeild as long as I fill canopy. 400 watts out the wall = 900 watt LED. Why you think everyone makes 600-1200 watt LEd and everyone uses 1000 watt standard HPS?
The seedbanks base their yeild this way. So what I do is double the energy of what is standard..
My 4x8 is 1900 watts out the wall. I only need technically 800 watts but again, that's based on HPS grow probably as most seedbank use non LEd methods. So I double up just in case. Then fill canopy with LST super cropping, cloning flowers, topping.. anything to get enough tops where I feel like once I flower, it'll fill in the whole space..
I guarantee myself max yeild this way without wondering if my math, my lights and space work together...