Quantitative Risk Register: How to Aggregate Risk & Size Contingency

This approach takes your understanding of quantified risks, measurements, and the use of probability distributions to build robust models that provide a clearer picture of your project's future.

We're making a significant shift from relying on simplistic singular planned values (like a project budget of $100 million which "doesn't consider all of the other alternatives or all those other... differences that happens that or risks that may happen that may affect this value eventually") or mere qualitative risk lists.

Our journey into effective Quantitative Risk Assessment begins with a crucial tool: the Quantitative Risk Register.

In project management, it's common to set a single planned value, such as a budget of $100 million for a project.

However, this singular value is inherently limited. It "doesn't consider all of the other alternatives or all those other... differences that happens that or risks that may happen that may affect this value eventually".

A single number fails to provide a realistic or comprehensive picture of what could truly happen. This is precisely where the power of an aggregated, quantified risk register, as part of a comprehensive Quantitative Risk Assessment, comes into play.

At its core, Quantitative Risk Assessment moves us beyond a simple list of risks.

It's about taking those identified uncertainties and assigning quantified values to them.

The first crucial step in this process is always to "identify the uncertain inputs".

These are things that are not fixed, like the quantity of excavation or the productivity rates of welding crews.

The main objective of building a Quantitative Risk Register as part of your assessment is to create an "aggregated risk register that has quantified values".

This allows us to "easily use it to quantify what is the overall risk level that we are currently facing". Instead of just knowing what the risks are, we now understand their combined potential impact.

To achieve this aggregated view, Monte Carlo simulation is key. Its "beauty" lies in performing "thousands and thousands of iterations" – as if you are doing the same project "10,000 times and every time we get a different budget every time, we get a different schedule".


These uncertain inputs, defined with "estimated range of values" and "probability distribution", are fed into a "Monte Carlo simulation engine" that generate for us "thousands of scenarios".

This powerful simulation is the engine that drives the quantification within a comprehensive Quantitative Risk Assessment, ultimately offering a "holistic picture about what the current situation is". For schedule-driven projects, see our schedule contingency reserve sizing guide.

Sizing Contingency and Reserves with Confidence Through Quantitative Risk Assessment