Factorio
Belt & Assembly Opt
Factorio ratios are the difference between a line that runs continuously and one that starves half the time, and the arithmetic gets awkward quickly.
How this is calculated
Every recipe has a crafting time and an input list, and every assembler tier has a speed multiplier. The calculator works out how many assemblers of each tier are needed to saturate a given output rate, and what input rate that demands upstream.
The arithmetic
- effective speed = assembler speed × (1 − 0.05 × productivity modules)
- items per craft = recipe output × (1 + 0.04 × productivity modules)
- assemblers = ceil((target rate × craft time) ÷ (items per craft × effective speed))
What people get wrong
Belt throughput is the constraint people hit first. A ratio that is mathematically correct still stalls if the belt feeding it cannot carry the required items per second, so check the belt tier against the input rate before building the row out.