Build Planner tells you exactly what to build.

Pick any item and how many you want per second. Build Planner shows the full production chain:

• Every ingredient and how much of it you need per second
• How many furnaces, assemblers and miners to build
• How much coal your burner furnaces and drills will eat
• An "Other options" column comparing other machines (for example, Assembling machine 2 vs 3)

How to use: click the button at the top-left of the screen to open the calculator.

Works with Space Age and other mods: it reads recipes straight from the game.
Doesn't count modules, beacons or productivity research yet.