Project Management guide

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What is the S-Curve in Project Management?

In project management terms, an s-curve is a mathematical graph that depicts relevant cumulative data for a project—such as cost or man-hours—plotted against time. The reason it’s called an s-curve is because the shape of the graph typically forms a loose, shallow “S.” (The shape depends on the type of project, though, so other formations are possible.)An s-curve in project management is typically used to track the progress of a project. In today’s fast-paced business climate, ensuring that a project is on schedule and on budget is paramount to its success.

Why an “S”?

The s-curve often forms the shape of an “s” because the growth of the project in the beginning stages is usually slow: The wheels are just beginning to turn; team members are either researching the industry or just starting to engage in the first phase of execution, which can take longer at first, before they get the hang of it or before there are kinks to work out.

Then, as more progress is made, the growth accelerates rapidly—creating that upward slope that forms the middle part of the “s.” This point of maximum growth is called the point of inflexion. During this period, project team members are working heavily on the project, and many of the major costs of the project are incurred.After the point of inflexion, the growth begins to plateau, forming the upper part of the “s” known as the upper asymptote—and the “mature” phase of the project. This is because the project is mostly finished at this point and is winding down: Typically only tasks such as finishing touches and final approvals are left at this point.

Common uses for the s-curve in project management

Some of the most common uses for s-curves are to measure progress, evaluate performance and make cash-flow forecasts.

An s-curve is helpful in monitoring the success of a project because actual, real-time cumulative data of various elements of the project—such as cost—can be compared with projected data. The degree of alignment between the two graphs reveals the progress—or lack thereof—of whichever element is being studied. If corrections need to be made to get back on track, the s-curve can help identify them.

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