Project Risk Score Calculator
Quantifies a project risk by combining its likelihood and potential impact into a single score out of 100. Use it during risk planning sessions to prioritise which threats need immediate mitigation.
About this calculator
The Project Risk Score is a standard risk matrix calculation drawn from frameworks like PMI's PMBOK and ISO 31000. The formula is: Risk Score = probabilityScore × impactScore. Both inputs are rated on a scale of 1 to 10, where 1 is very low and 10 is very high. Multiplying them together produces a score between 1 and 100. Scores are typically banded into three zones: low risk (1–25), medium risk (26–60), and high risk (61–100). This numerical approach removes the subjectivity of purely qualitative labels and lets project managers rank multiple risks side by side. Reassessing scores regularly as the project progresses is essential, because both probability and impact can shift as circumstances change.
How to use
Imagine you identify a risk that a key supplier might deliver materials late. You rate the probability at 7 out of 10 because the supplier has missed deadlines before. You rate the impact at 8 out of 10 because a late delivery would delay the entire project launch. Step 1 — Multiply: 7 × 8 = 56. Your Risk Score is 56, which falls in the medium-to-high range. This signals that you should create a concrete mitigation plan — for example, securing a backup supplier — rather than simply monitoring the risk passively.
Frequently asked questions
What do different project risk score ranges mean for my project?
Scores from 1 to 25 are generally considered low risk and can be accepted or monitored with minimal action. Scores from 26 to 60 fall in the medium range and typically warrant a documented response plan. Scores from 61 to 100 are high risks that demand immediate mitigation strategies and assigned owners. These thresholds are guidelines; your organisation may calibrate its own bands based on risk appetite and industry standards.
How should I rate probability and impact scores accurately?
Probability should reflect the realistic likelihood of the risk event occurring, informed by historical data, expert judgment, or analogous projects. Impact should reflect the severity of consequences on project objectives such as schedule, budget, scope, or quality. Using a defined rating rubric — for example, 1–2 means negligible, 3–4 means minor, and so on — ensures consistency across your team. Calibration workshops where multiple stakeholders score independently and then discuss discrepancies improve accuracy significantly.
Why is multiplying probability by impact better than adding them together?
Multiplication captures the compounding relationship between the two dimensions more faithfully than addition. A risk with probability 1 and impact 10 added together gives 11, the same as probability 6 and impact 5, yet those are very different risk profiles. Multiplying gives 10 versus 30, correctly distinguishing a rare catastrophic event from a moderately likely moderate event. This non-linear scaling is why the multiplicative risk matrix has become the industry standard in project management frameworks worldwide.