Risk Matrix Score Calculator

Work out risk matrix score instantly with clear inputs, formula shown and shareable results.

About Risk Matrix Score Calculator

A five by five risk matrix multiplies likelihood by severity to give an inherent score from one to twenty-five. Applying an effectiveness factor for existing controls gives the residual score, which is what determines whether work may proceed. Scoring inherent and residual risk separately makes the value of the controls visible.

Formulas

Risk score

Inherent = likelihood x severity; residual = inherent x (1 - control effectiveness)

Bands

Very low below 3, low 3-4, moderate 5-9, high 10-14, extreme 15 and above

Worked example

With the default values below, Risk Matrix Score Calculator returns Residual risk score of 6.40. Change any input above and every figure here is recalculated in your browser.

Inputs used

Likelihood scoreaccepts 1–5: 4
Severity scoreaccepts 1–5: 4
Effectiveness of existing controlsaccepts 0–95 %: 60 %

Results

Residual risk score: 6.40
Inherent risk score: 16
Risk level: Moderate
Action required: Implement additional controls within a defined timescale

Step by step

1Values used
2Risk score
3Bands
4Residual risk score= 6.40
5Inherent risk score= 16
6Risk level= Moderate
7Action required= Implement additional controls within a defined timescale

Assumptions and limits

The result is derived only from the 3 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 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
Preliminary estimate only. Risk assessment must be carried out by a competent person using the matrix and criteria adopted by your organisation.

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

Preliminary estimate only. Risk assessment must be carried out by a competent person using the matrix and criteria adopted by your organisation.

Frequently Asked Questions

How is the Risk Matrix Score figure worked out?

Inherent = likelihood x severity; residual = inherent x (1 - control effectiveness). A five by five risk matrix multiplies likelihood by severity to give an inherent score from one to twenty-five.

Why never score controls as fully effective?

No control is perfect and all can be bypassed, degrade or be misapplied. Capping effectiveness below 100 percent forces the residual risk to remain visible and monitored.

What values do I need to enter?

This calculator takes 3 inputs: Likelihood score, Severity score, Effectiveness of existing controls. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.