I just make labs and factories in arbitrary amounts, and then adjust the amounts later as I go based on where I see the bottlenecks. I tried getting the ratios

I just make labs and factories in arbitrary amounts, and then adjust the amounts later as I go based on where I see the bottlenecks. I tried getting the ratios exactly right up-front when I first started playing, but it was almost never worth the effort because I would usually outpace the production of a specific input resource (especially when I later built new factories that used one of those inputs too).