5×5 Risk Matrix Calculator

Score any hazard the way UK construction risk assessments do: rate the likelihood of harm (1–5, rare to almost certain) and the severity if it happens (1–5, negligible to catastrophic). Multiplying them gives a rating from 1 to 25 that maps to a band with a clear action.

The Bands and Their Actions

  1. 1–4 Low — manage through routine site controls and normal supervision; reassess if the task or conditions change
  2. 5–9 Medium — plan and implement additional controls with a named owner and timescale; supervise existing controls in the meantime
  3. 10–15 High — significant additional controls required before work proceeds, verified by a competent person on site
  4. 16–25 Very High — stop; redesign the task to remove or substitute the hazard, with senior sign-off before anything proceeds

Organisations draw these boundaries slightly differently — what matters is that they are defined, applied consistently, and paired with actions.

A Worked Example

Manual tile cutting with a petrol disc cutter and no water suppression: silica dust exposure is likely (4) with major long-term harm (4) — an inherent rating of 16, very high: redesign the task. Switch to a cutter with water suppression plus RPE and likelihood drops to unlikely (2) while severity stays major (4) — a residual rating of 8, medium: proceed with the controls documented and supervised. That before/after pair is exactly what a reviewer wants to see in a RAMS hazard register. Note the common scoring error the example avoids: controls reduce likelihood, but they rarely change what the harm would do, so severity usually stays put.

Scoring is step one — the document is the deliverable. Generate a full risk assessment | All free tools