Risk Assessment Matrix

A risk assessment matrix is a simple visual tool used to prioritise risks based on how likely they are to happen and how severe the consequences could be. This article explains how a risk assessment matrix works and includes a practical 5×5 matrix you can use to assess risk levels quickly and consistently.

If you need a clear way to decide which risks require immediate action and which can be monitored, a matrix helps turn judgement into a structured decision.

What is a risk assessment matrix?

A risk assessment matrix is a chart that combines two factors:

• Likelihood – how probable it is that a hazard will cause harm

• Severity – how serious the harm would be if it occurred

By plotting likelihood against severity, the matrix produces a risk rating. This rating helps you prioritise controls, resources, and actions.

A matrix does not replace a full risk assessment. It supports it by making risk levels easier to compare and justify, especially when multiple hazards are involved.

What is a 5×5 risk assessment matrix?

A 5×5 risk assessment matrix is one of the most commonly used formats. It uses:

• Five likelihood levels, typically ranging from “rare” to “almost certain”

• Five severity levels, typically ranging from “minor injury” to “fatal or catastrophic harm”

Each likelihood score is multiplied by each severity score to produce a risk rating, usually from 1 to 25.

The matrix is often colour-coded to show which risks are acceptable, which require action, and which must be addressed immediately.

How the 5×5 risk assessment matrix works

The matrix works in three steps:

1. Score the likelihood
   Decide how likely the hazard is to cause harm, based on experience, controls already in place, and exposure.

2. Score the severity
   Decide how serious the harm could be if the hazard occurred, assuming controls failed.

3. Find the risk rating
   Where the likelihood and severity scores meet on the matrix, you’ll see a risk level and an associated action.

This approach supports consistent decision-making, especially across teams or sites.

Using the risk assessment matrix image on this page

The matrix image above is designed to function as a practical reference tool.

• The horizontal axis shows likelihood, with plain-English descriptions alongside numerical scores.

• The vertical axis shows severity, again using both numbers and descriptors.

• Each cell displays:

  • The combined risk score

  • A clear action outcome, such as “Monitor”, “Reduce risk”, or “Stop activity”

You can use the matrix during risk assessments, toolbox talks, or planning sessions to agree risk priorities without additional software

What do the risk ratings mean?

While wording varies by organisation, risk ratings are typically interpreted as follows:

• Low risk
  Acceptable with existing controls. Continue to monitor.

• Medium risk
  Additional controls may be required. Plan and implement risk reduction measures.

• High risk
  Action required urgently. Work should not continue until risk is reduced.

• Very high or intolerable risk
  Stop the activity immediately. Redesign the task or eliminate the hazard.

The value of the matrix is consistency, not mathematical precision. It helps teams agree priorities rather than predict outcomes.

When a risk assessment matrix is useful

A risk matrix is particularly useful when:

• Comparing multiple hazards across a task or site

• Prioritising actions where resources are limited

• Explaining decisions to workers, managers, or clients

• Supporting documented risk assessments with a clear rationale

It is commonly used alongside general risk assessments, method statements, and RAMS documentation.

Limitations of risk assessment matrices

Risk assessment matrices have limitations that should be understood:

• Scoring can be subjective

• Different people may rate the same risk differently

• Complex or rapidly changing risks may need more detailed analysis

For higher-risk activities, a matrix should support not replace detailed planning, supervision, and control measures.

Risk assessment matrix and UK health and safety expectations

UK health and safety guidance focuses on proportionate risk management. A matrix can help demonstrate that risks have been considered logically and consistently, but it does not remove the need to:

• Identify hazards properly

• Implement suitable control measures

• Review risks when circumstances change

Used correctly, a risk assessment matrix supports clear, defensible decision-making.

Conclusion

A risk assessment matrix is a practical way to prioritise hazards by combining likelihood and severity, helping you decide where action is needed most. Used correctly, it brings consistency and clarity to risk decisions, but it still relies on accurate information, regular review, and clear documentation.

For organisations that need to record, review, and update risk assessments efficiently, using a digital risk assessment system can help turn matrix-based decisions into structured, auditable actions. Our risk assessment software supports this process by helping teams document hazards, apply controls, and keep assessments up to date as work changes.