S Curves in Project Management | A Practical Approach

What is an S Curve in Project Management?

Definition: Graphical representation of quantities like cumulative costs, labor units etc. plotted against time.

An S-Curve is one of the major tools used in Project Management that tracks project progress over time. It is a graphical representation that gives the required information in a flash.

Hence all the Project Stakeholders always demand to have these s-curves in the reports as it helps them to get the project status without any hassle.

What are the Elements for an S Curve?

It is clear by definition that it is a graph & you know to draw a graph we must need at least two coordinated values to plot against each other. Here, time is common in every S-Curve.

To understand in a better way, let’s discuss some the most common S-Curves used in Project Management below;

Typical S Curve
Typical S Curve for Projects

 

You can see at start it is quite flat and so at the end but steeper at middle, is typical of most projects.

The curve represents the cumulative work done over time & hence the steepness or flatness gives us the rate of work over time.

It is clear at initial stage you need less resources but in middle we call it execution phase needs maximum of all the resources. The end is same as the initiation phase.

Uses of S Curves

As I am working in Project Controls and my Project Manager is always demanding to show every possible data in the form of S – Curves like my weekly and monthly reports include following S-Curves;

  • Baseline S-curve
  • Baseline Ranges (Banana Curves)
  • Man-hours Vs Time
  • Recovery Plan Vs Actual
  • Cash Flow – Plan & Actual & Forecast
  • Quantity Comparisons
  • Progress and Performance Evaluation
  • Manpower Histogram
  • Percentage S-curves

It’s great way to monitor project performance, variance & ultimately forecast to achieve the required goals. You can have all history, current status & forecasting at one graph. S-Curves are easy to communicate & give clear indications about the health of the project.

 Practical Examples of S-curves

To understand better that how to read S Curves, let me explain the below fig. scenario,

At particular date we call it as Data Date or Cut of Date the Actual Progress is below the Baseline Value and that difference is called Variance.

As you know There are three common project tracking methods are

  1. Man-hours
  2. Cost
  3. Quantity

 Now, the Project Manager needs to look at and either need to increase the resources we call it Crashing or he needs to Fast Track the activities that may leads to Risk issues. But he needs to act upon any of these to increase work rate as overall project health is not acceptable for that particular time. He can use both simultaneously.

 

A Typical S Curve
Progress Performance Evaluation Through a Combination of S Curves

 

Real Case Study for Understanding S-Curves

Now, once everything is analyzed then we may need to submit a recovery plan also called a mitigation plan showing that how we are going to catch-up the delays.

These curves are not like as we have seen the typical one but this may happen in practical scenarios. Here the client has asked to hand over a few major areas even in the middle of the project. That leads to differ the work rate as in typical s curves scenarios.

As you see, the Green & Red are representing the Early Units and Late Units respectively. The combination of both gives us a Banana Curve. It helps us if the project slips below the Red zone then it is alarming thing that should be fix immediately without any delay.

This is real example where we were asked to submit Recovery Plan where we were slipping below the Red line, you can see the Blue like for actual work. We acted upon immediately and submitted our action plan that included the increase in manpower, expedition of required critical materials delivery, fast tracking of a number of activities. We presented this to Stakeholders, performed and the day I am writing this blog we are as per our recovery plan without any negative Variance.

Man-Hours Versus Time S-Curve

Below is the graphical explanation that how we increased the manpower to catch up the above delays for that particular project. No doubt there is a huge difference in planned, actual & of the recovery. This may be because we over estimated the Productivity Rates. As we were delayed in some critical material then we have to deployed the other skilled manpower simultaneously and some of our manpower become idle for time being – waiting for material to be procured & to be delivered onsite.

Manpower Histogram
Manpower Histogram – Month Wise

How an S-Curve is Generated?

First of all, we need to have over baseline plan. From this we can generate early start & early finish S-curves. You know combination of both is called a Banana curve. This baseline program can be prepared in a number of planning software like Primavera P6, MS Project and Asta, Tilos, SAP etc. These may give you S Curves directly or you need to use some third-party application like Microsoft Excel to get it done after exporting data.

I normally use Primavera P6 and used to export data in MS Excel as it gives me freedom to use required visualization that is necessary to present to top management. Before doing I prefer to see the result in Primavera P6 so that if there is any issue with it as in Primavera you can get S Curves of almost every type.

Conclusions

S Curves are one of the most valuable Project Management Tools for reporting a project. As it is best way to communicate to the Stakeholders and you know better communication is the key to success of any project.


That’s all. Thank you to bear with me. If you have any suggestion for improvement of this blog please comment below. I will try to fill that gap where possible.


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