Risk matrix calculator
Pick a likelihood and severity from one to five — on the matrix or with the labelled selects — to get the risk score, its band and what that means for your RAMS. Add a residual score to show the risk before and after your controls.
Free to use — no signup, nothing stored. Your details stay in your browser.
Checked against HSE thresholds
result updates as you add entries
Initial risk
Score the risk before any controls are applied — how bad it could be and how likely it is as the task stands.
| Likelihood → | ||||||
|---|---|---|---|---|---|---|
| 1 | 2 | 3 | 4 | 5 | ||
| Severity → | 5 | |||||
| 4 | ||||||
| 3 | ||||||
| 2 | ||||||
| 1 | ||||||
6 June 2026
| Hazard | Not specified |
| Initial rating | 3 × 3 = 9 (Medium) |
The score is a prioritisation aid only. It does not, on its own, make the work safe or compliant — a competent person must review the rating and controls for the specific task and site.
How the 5×5 risk matrix works
A 5×5 risk matrix is the scoring method most UK construction risk assessments and RAMS documents use. You rate each hazard on two scales of one to five — how likely the harm is, and how severe it would be — then multiply them:
Risk score = Likelihood (1–5) × Severity (1–5), giving a number from 1 to 25.
The score puts the hazard into a band so you can decide how urgently to act and how strong the controls need to be. It is a way of prioritising hazards consistently — not a measurement that, by itself, makes the work safe or compliant.
The band thresholds used here
This calculator uses the same bands as the RamsDocs RAMS builder, so a score here matches what you would see in a generated risk assessment:
- 1–4 — Low. Generally acceptable. Keep existing controls in place and review if the task or site changes.
- 5–9 — Medium. Tolerable only with documented controls. Reduce the risk as far as is reasonably practicable and brief the team.
- 10–15 — High. Act before work starts. Further controls are needed; the work should normally only go ahead once it sits in a lower band.
- 16–25 — Very high. Stop. Do not proceed until the hazard is eliminated or the task is redesigned and re-assessed.
Different organisations draw the band lines in slightly different places — always follow the matrix agreed by your own competent person or principal contractor where one is specified.
Likelihood and severity definitions
| Score | Likelihood | Severity |
|---|---|---|
| 1 | Rare — extremely unlikely | Negligible — first aid only |
| 2 | Unlikely — not expected but possible | Minor — short absence |
| 3 | Possible — might happen occasionally | Moderate — over a week off work |
| 4 | Likely — will probably happen | Major — serious injury or long-term harm |
| 5 | Almost certain — expected, often | Catastrophic — fatality or multiple serious injuries |
Initial and residual risk
Good practice — and what most principal contractors expect — is to record the risk twice: the initial rating before controls, and the residual rating once your control measures are in place. The drop between the two shows that the controls actually reduce the risk. Use the residual section above to score both and see the before-to-after change.
What the score does and does not tell you
A low number does not mean a hazard is harmless, and the matrix cannot capture everything — where a fatality or major injury is a plausible outcome, treat it seriously even if the calculated score looks modest. Scoring is a prioritisation aid that must be reviewed by a competent person against the specific task and site; it is not, on its own, a compliance outcome or a sign-off that the work is safe.
For the underlying method, see HSE's guidance on how to do a risk assessment.
RamsDocs helps draft structured RAMS from your job details. It does not replace competent-person review, site-specific judgement or your legal duties.
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