Most people struggle when they’re asked to estimate the time they need to complete a project. Some people error on the side of pessimism, quoting far too much time, while others are too optimistic, leading to missed deadlines and unhappy clients.
Being able to estimate the amount of time required to complete a task is a skill that every project manager should have. In fact, project managers are almost wholly graded based on their ability to see a project to it’s timely completion.
It’s impossible to know how much time a task will require if you don’t first understand the true scope of the task. Often, projects are late not because of lack of effort, but because the details of the project were not properly identified and prioritized. Once you know the tasks, it is up to the project manager to include the necessary parties involved in the estimation process. The person who will be doing the work will always have the most accurate estimation.
When you look at a project as a whole, it’s often difficult to conduct a true analysis of the requirements. This is especially true for large projects. Breaking down your project means segmenting all of the different moving pieces into so-called “mini projects”. From there, you can allocate small portions of time to certain aspects of the project. Finally, you add together the projected time of all of the mini projects, resulting in a more accurate final duration length. By narrowing the scope to these single “events”, you will be able to provide a better overall estimate.
For an example, I will use a website project. A client contacts you and asks for you to quote him on a time span to complete his site. You could go out on a limb or reference past projects as the standard deviation. Or you could break the project down into the individual pages. “The header and footer will take two hours. The home page five. The about, services and contact page should each take about three hours each. In total, that comes to 16 hours.”
PERT stands for Project Evaluation and Review Technique. It’s a project estimation technique used by thousands of organizations around the world.
Many top organization employ mathematical formulas to estimate a task or activity. While there is some science involved, most of the effectiveness comes from the psychological effect that using a cold calculation can provide. I prefer to use the PERT formula, for it’s simplicity and accuracy.
In order to use PERT, you must first identify three simple estimates:
Now apply the following formula:
Voila! Now you have a fairly accurate estimate based on mathematical calculation, not emotion, greed or guilt.