1. A computer-implemented method of estimating risk in financial metrics of a business case, comprising: categorizing each financial metric into a plurality of risk factors; receiving likelihood of risk associated with each risk factor in first categorical scale; receiving severity associated with each risk factor in second categorical scale; converting said first categorical scale and said second categorical scale into numerical scale using a mapping; determining, by a processor, a maximal threshold parameter K that represents at most K risk factors that simultaneously impact the business case with at least a threshold probability A; determining net relative impact using an aggregation function, Δ ( i 1 , i 2 , … , i I ) = 1 - ( ∏ k = 1 I ( 1 - Δ k ) ) ∀ 1 < I ≤ K , wherein K=risk factors that can simultaneously impact corresponding business case; determining combinatorial subsets of the K risk factors; determining net severity impact for the combinatorial subsets using the aggregation function; determining risk likelihood for the combinatorial subsets; and converting the net severity impact for the combinatorial subsets and the risk likelihood for the combinatorial subsets into probability distribution.