Project Management Life Hacks – PERT Estimates

By: Kim Kiefer ConvergeSecure® Project Manager

As a project manager, I must be able to produce and deliver budgets and schedules that are not only accurate but also contain an acceptable allowance for risk (both positive and negative).

This is achieved through various estimating techniques from very basic to so complex I need a software program to crunch the numbers for me. But there is one technique where the accuracy is surprisingly high considering how little math is involved – PERT estimating.

PERT (Project/Program Evaluation and Review Technique) was first developed by the United States Navy in the 1950’s to simplify the planning and scheduling of large and complex projects, specifically the Polaris nuclear submarine project.

PERT is basically a three-point estimate that considers the pessimistic, optimistic, and a weighted most likely estimate. In project management, these data points can be used in additional techniques and simulations to further refine accuracy and probability, but the initial, basic equation can help in any situation where you need to estimate something when you don’t have a lot of information and there are risk variables to consider.

You will note that M, the most likely, is multiplied by four to give that estimate the most weight in the equation.

You then divide by six instead of three because there are six data points (O + M + M + M + M + P).

Admittedly, this process is only as accurate as the data you have going in, but even the roughest estimates can help.

Example: For vacation this year, you decide you are driving to Florida rather than flying and you need an idea of how long it will take. Google Maps tells you that it will take 18 hours (without stops). You estimate ten hours for meals, four hours for miscellaneous stops, and ten hours for one night in a hotel. Your estimate is 42 hours. Worst case scenario? Weather is horrible and your fastest route turns out to be under construction. Now your original estimate doubles to 84 hours.

What is a realistic estimate?

Now that you estimate your drive time at 45 hours you can plan the time needed for the whole trip.

This works great for budgeting as well. It is sure to give you that little “just in case” cushion so you are not caught off guard if things don’t go as planned.

The PM (Project Manager) is a critical player in our implementation stage. After Our Process of learning about your business and designing an optimal solution, they are the individual charged with ensuring its deployment is done not only correctly, but also in the most efficient manner and with minimal disruption to you as our customer.   

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