SIL Safety Integrity Level - Online Calculator

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🔐 SIL Safety Integrity Level

Required SIL for a SIF from the Risk Reduction Factor (RRF) or PFDavg (IEC 61511)

SIL Determination

Method

Risk Reduction Factor RRF (unmitigated frequency / tolerable frequency)

SIL Levels (IEC 61511)

SIL	PFDavg (probability of failure on demand)	RRF	Description
Below SIL 1	> 1×10⁻¹	< 10	Generally no SIL management required
SIL 1	1×10⁻¹ ~ 1×10⁻²	10 ~ 100	Risk reduction 10~100x
SIL 2	1×10⁻² ~ 1×10⁻³	100 ~ 1000	Risk reduction 100~1000x
SIL 3	1×10⁻³ ~ 1×10⁻⁴	1000 ~ 10000	High-risk scenario; redundant architecture + high diagnostic coverage required
> SIL 3	≤ 1×10⁻⁴	≥ 10000	Multiple independent SIFs or special design recommended

· Architecture reference: basic 1oo1 typically reaches SIL 1~2; 1oo1 with diagnostics, or 1oo2 / 2oo3, can reach SIL 2~3.

SIL calculator per IEC 61508/61511: compute PFDavg and risk reduction factor, then map to SIL 1-4 requirements for SIF rating.