S CURVE

The S curve is a line chart that shows the planned versus actual cumulative costs for a project. The difference between the planned and the actual lines plotted on the chart indicates a positive or negative cost performance. Ideally, the planned and actual should match. The S curve can be plotted for individual groups of tasks or for an entire project.

The S curve offers several benefits. It allows you to determine the overall cost performance for a task, resource, or entire project. It also provides the means for anticipating potential cost problems in the future. Finally, it provides an audit trail on the overall performance of a project.

for Constructing and Using an S Curve

• Draw a horizontal line (x-axis) reflecting a time continuum (e.g., days, months).
• Draw a vertical line (y-axis) reflecting the graduated cumulative costs for your project.
• Plot the planned cumulative cost for the project at periodic time intervals (e.g., weekly).
• Connect the planned plots using a dotted line.
• As data are accumulated, plot the cumulative cost for a specific point in time.
• Connect the actual plots using a solid line.