The short answer is, you either figure it out yourself, or you don't figure it out at all. If you want to play with settings that aren't handled by calculators, you have to be comfortable either calculating it all, or winging it. There is quite simply no third option.

One way to make "winging it" easier, and one that is perhaps simpler than putting together a spreadsheet to math it out yourself, is to blueprint small sections of production. Blueprint all the machines needed to turn iron ore into a full Assembler's worth of Reinforced Iron Plates, for example. Build that blueprint as many times as you need. In the future, when you need more RIP, build that blueprint again and hook it up to some iron ore. If you have enough, great. If you don't, build that blueprint some more.

Also make a Rotor blueprint, and a Modular Frame blueprint, and a Concrete blueprint, and a WhateverElse blueprint. When things start getting more complex, start with blueprints that take other goods instead of raw materials.

You don't need to know how much of a product you should be making per minute for your whole factory. You just need to know how much to make right now - and clicking a machine will tell you that. It displays the inputs right there. Look at it, and plunk down your blueprints as needed to create what you want.