Control Effectiveness Score Calculator

Work out control effectiveness score instantly with clear inputs, formula shown and shareable results.

About Control Effectiveness Score Calculator

A simple pass rate treats a partially effective control as a failure and a critical control failure as equal to a trivial one. Weighting partial results at half credit and deducting for critical failures produces a score that moves when it should: three critical failures pull the environment out of the strong band even when the raw pass rate looks healthy.

Formula

Weighted effectiveness

score = (effective + 0.5 x partial) / tested x 100 - 5 x critical failures, floored at 0

Worked example

With the default values below, Control Effectiveness Score Calculator returns Weighted control effectiveness of 71.3%. Change any input above and every figure here is recalculated in your browser.

Inputs used

Controls testedminimum 1: 120
Controls operating effectivelyminimum 0: 96
Controls partially effectiveminimum 0: 15
Failures on critical controlsminimum 0: 3

Results

Weighted control effectiveness: 71.3%
Simple pass rate: 80.0%
Controls that failed outright: 9
Control environment rating: Significant deficiencies

Step by step

1Values used
2Weighted effectiveness
3Weighted control effectiveness= 71.3
4Simple pass rate= 80.0
5Controls that failed outright= 9
6Control environment rating= Significant deficiencies

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 1 decimal place, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Should design and operating effectiveness be scored separately?

Yes. A well-designed control that is not operating is still a failure, but the remediation is entirely different from redesigning a flawed control.

How large should a test sample be?

It depends on control frequency. Common audit guidance is 25 to 60 samples for daily controls and full population testing for annual ones.