S Curves 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.

Sample: Excel Template for S Curves  for Manpower Histogram

Related: Work Breakdown StructurePrimavera P6 Download & Install | Free & Legal Copy

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 of the most common S-Curves used in Project Management below;

Typical S Curve
Typical S Curve for Projects

You can see at the start it is quite flat and so in the end but steeper in the 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 the initial stage you need fewer resources but in middle, we call it execution phase needs the maximum of all the resources. The end is the same as the initiation phase.

Uses of S Curves

The best use of S curves is in Earned Value Management. A tool that helps the project manager and the team to understand the variance is any project in no time.

Earned Value Management

Earned value management system uses historical data to forecast the future.

Let us see how a combination of s curves help in determining the project important scenarios like;

  • The project is on budget
  • The project is on schedule

Earned value management helps to find out the slippages that ultimately alert the team to negotiate. It is a complete set of ongoing project information that tracks in the best possible scenarios. And more importantly, through S curves anyone in the team can understand the status in a flash.

Below is the infographics representation to understand the system easily.

Earned Value Management System

From this you can easily calculate;

Schedule Performance Index – SPI 

SPI = EV/PV, if

  • SPI<1, the project is behind schedule
  • SPI=1, the project is on schedule
  • SPI>1, the project is ahead of schedule

Cost Performance Index – CPI

CPI = EV/AC, if
  • CPI<1, the project is over budget
  • If CPI=1, the project is on budget
  • CPI > 1, the project is under budget

The same way we can calculate and drive the forecast from other formulas like,

EAC – Estimate at Completion = 

  • AC + (BAC – EV)
  • AC + [(BAC – EV)/(SPI x CPI)]
  • AC + ETC

ETC – Estimate to Complete = 

  • EAC – AC
  • New Estimate

VAC – Variance at Completion = BAC – EACTCPI – To Complete Performance Index =

  • (BAC – EV) / (BAC – AC)
  • (BAC – EV) / (EAC – AC)

More S Curves on a Project

Also, 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 a 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 CurvesTo understand better than 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

  • Man-hours
  • Cost
  • Quantity

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

Progress Performance Evaluation Through a Combination of S Curves explained
Progress Performance Evaluation Through a Combination of S Curves

Real Case Study for Understanding S-CurvesNow, 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.s curve in a real project management
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 differing the work rate as in typicals 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 an alarming thing that should be fixed immediately without any delay.This is a real example where we were asked to submit Recovery Plan where we were slipping below the Redline, you can see the Blue like for actual work. We acted upon immediately and submitted our action plan that included the increase in manpower, an 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 overestimated Productivity Rates. As we were delayed in some critical material then we have to deploy 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 for a Project including S curves
Manpower Histogram – Month Wise

How an S-Curve is Generated? First of all, we need to have over a baseline plan. From this, we can generate early start & early finish S-curves. You know a 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 the 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 an issue with it as in Primavera you can get S Curves of almost every type.

Wrap Up

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

One Small Request: Being a Project Management guy, I know how little time we have to play around on the internet. But if you have found this information useful then please share it to your colleague so that more people can get benefit from it. If you have any question then comment below and I am glad to take it.

Further Reads: If you think it a good read then share with your colleague & also visit here

15 thoughts on “S Curves in Project Management”

  1. Thank you very much for explaining the stuff through practical experience. Would love to know more about how to draw it in MS Excel or if you can provide any template – Much appreciated.
    Keep up good work.

    1. Thanks for coming on my blog. First comment is always a lit to any blogger. Regarding your query, you can go to “Downloads” section and can get desired templates. If you need another as well please ping me again. I will try my best to arrange.
      Here is the link for your convenience https://whydoitrain.com/downloads/

  2. Thanks You Mate! I am blogger too but I love when you use practical experience. I suppose you have a good command on Project Management field. Keep Rocking!!

    1. Thank you! Mate I would love to read your blogs too. Please share and also don’t hesitate if you have any suggestion for improvement.

  3. Nice read! Thank you team for writing this piece based on some practical illustrations. Looking forward to know about Lean Project Management. Can you please write-up!

  4. Thank you team for sharing this insightful experience. Practical s curve graphs gives confidence when developing these curves as most books have smooth curves which is not normally when you go and apply practically.

  5. A good read dear. Thanks for write up. Would be nice if you could elaborate how to make s curve in MS Excel or refer ant video. A real blogger behind.
    A bit grammar need to improve though. But natural you are.

  6. Thanks you dear
    I just shared it with my colleagues. Practical nature of S curve is not like smooth always – Good to know

    1. S Curves are best to understand execution stuff in Project management especially I guess 🙂 If you need to know more about Project Management – Stay tuned!

  7. Hello,
    I really value what your doing. Its excellent. I try to send you an email but it was send back to me. i would be happy to be able to send you an email.

  8. Earned value management always confuses me. Can you please write on it also? Though I got the idea from your post. Highly appreciated the good stuff on your website.

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