The S-curves in MS Project

There is always a lot to do about S-curves in MS Project. It is a greatly appreciated tool for managers to assess your projects status quickly.

The s-curves in MS Project1

An S-curve is defined as:

“A display of cumulative costs, labor hours or other quantities plotted against time. The name derives from the S-like shape of the curve, flatter at the beginning and end and steeper in the middle, which is typical of most projects. The beginning represents a slow, deliberate but accelerating start, while the end represents a deceleration as the work runs out.”

Source: Wideman Comparative Glossary of Common Project Management Terms v2.1 Copyright R. Max Wideman, May 2001

Before the 2013/2016 version of MS Project, it was not possible to get S-curves directly from the tool as it dit not supply cumulative values and as such was not capable of drawing these lines that build on information of earlier weeks. The 2013/2016 version is capable of doing that using the Reports tab of MS Project.

There are a variety of S-curves that are applicable to project management applications, including:

  • Hours versus Time – Interesting for labor-intensive projects, whereas man hours earn the project’s value.
  • Costs versus Time – If the project’s cost breakdown also contains a significant portion of non-labor components (materials).

S-curves can either show absolute values or relative values. Absolute would be expressed as 500 of the 1000 hours still to go, whereas relative values would be expressed as 50% of the work still to go, or 50% of the costs still to incur.

Usually S-curves would show three lines (curves)

  1. The baseline curve – how the work or costs would evolve according to the baseline
  2. The target (forecast) curve – how the work or costs are now scheduled to evolve
  3. The actuals curve – how the work or costs actually have evolved. Obviously, as the project is still progressing this curve is cut-off on a certain date. This is of course the status date

How is the S-curve report actually used?

Consider the following scenario’s:

  • The target (forecast) curve (your current schedule) compared to your baseline shows you more work than expected, this means you have to put in extra people to make up for delays caused by issues, holidays, sickness, etc.
  • The target (forecast) curve (your current schedule) compared to your baseline ends further to the right, this means that your project will be delayed if you do not take action.

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