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TABLE 2: RISK LIKELIHOOD SCORE: What is the likelihood of the consequence occurring
The frequency-based score is appropriate in most circumstances and is easier to identify. It should
be used whenever it is possible to identify a frequency.
The probability based score may be useful when rating risks associated with the success of timelimited
or one-off project. For example, a three-year project cannot be expected to fail ‘once a
month’, and the likelihood score will need to be assessed on the probability of adverse
consequences occurring within the project’s time frame.
Likelihood
score
1 2 3 4 5
Descriptor Rare Unlikely Possible Likely
Frequency
How often
might
it/does it
happen
Probability.
Will it
happen or
not
This will
probably
never
happen/rec
ur
Less than
0.1%
Do not
expect it to
happen/rec
ur but it is
possible it
may do so
Between
0.1 %and
1%
Might
happen or
recur
occasionally
Between
1% and
10%
Will
probably
happen/rec
ur but it is
not a
persisting
issue
Between
10% and
50%
Almost
certain
Will
undoubtedly
happen/rec
ur, possibly
frequently
Over 50%
TABLE 3: RISK RATING MATRIX
Risk scoring = consequence x likelihood
Consequence/
Impact score
Likelihood
1 2 3 4 5
Rare Unlikely Possible Likely
Almost
certain
5 Catastrophic 5 10 15 20 25
4 Major 4 8 12 16 20
3 Moderate 3 6 9 12 15
2 Minor 2 4 6 8 10
1 Negligible 1 2 3 4 5
The scores obtained from the risk matrix are assigned grades as follows
1 - 3 Low risk
4 - 6 Moderate risk
8 - 12 High risk
15 - 25 Extreme risk