The Risk Reduction Factor (RRF) is the inverse of PFDavg and gives an intuitive sense of “how much” the safety function reduces the unmitigated risk. RRF = 100 means the protection layer reduces risk by 100×.

This calculator is the bridge between LOPA (Layer of Protection Analysis) outputs — which directly produce required RRFs — and SIL band targets used in IEC 61511 specifications.