---
title: "Calculating and evaluating the Overall SIL"
slug: "calculating-and-evaluating-the-overall-sil"
tags: ["LOPA", "SIS"]
updated: 2026-10-27T23:12:18Z
published: 2026-10-27T23:12:18Z
canonical: "ims-handbook.cenosco.com/calculating-and-evaluating-the-overall-sil"
---

> ## Documentation Index
> Fetch the complete documentation index at: https://ims-handbook.cenosco.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Calculating and evaluating the Overall SIL

When all the [Initiating Events](/v414/docs/defining-initiating-events) and [Barriers](/v414/docs/defining-barriers-lopa) have been defined it is time to calculate and review the Overall SIL.

- Click the *calculate* button.
  - Note: It will show red ![](https://cdn.document360.io/e492a0e0-a4ba-4aca-8fc6-76b95f91fdf3/Images/Documentation/image-EQBE1HPV.png?sv=2026-02-06&spr=https&st=2026-10-28T16%3A48%3A25Z&se=2026-10-28T17%3A48%3A25Z&sr=c&sp=r&sig=sh1cc4qx13eVukwZvL89mOe5dcG51Nj%2BFyLmv4YwSno%3D) when a calculation is required.
- Evaluate the Overall SIL to assess the adequacy of the existing or proposed Barriers against the Hazard Scenario.
- If the Overall SIL for the Consequence is not acceptable, [start a SIF Analysis](/v414/docs/adding-sif-analyses-to-the-lopa) and determine the SIF’s minimum required RRF, i.e., its [Target PFD](/v414/docs/calculating-the-sif-analysis-target-pfd), that achieves an acceptable Overall SIL level.

![](https://cdn.document360.io/e492a0e0-a4ba-4aca-8fc6-76b95f91fdf3/Images/Documentation/calculating-and-evaluating-the-overall-sil-image-im86hdca.png?sv=2026-02-06&spr=https&st=2026-10-28T16%3A48%3A25Z&se=2026-10-28T17%3A48%3A25Z&sr=c&sp=r&sig=sh1cc4qx13eVukwZvL89mOe5dcG51Nj%2BFyLmv4YwSno%3D)

After calculation, review the Overall SIL.

Take Note

- It is possible to batch calculate LOPAs.
- Recalculated SIFs will revert to Draft if the SIL level of the SIF Analysis changes or if a new version of the LOPA is created.
- To perform a batch LOPA calculation, please [contact Cenosco Support](/v414/docs/requestingsupport), as this feature is not yet available to the end user.