
If you are a project manager, you may have heard of S-Curve, which shows progress, cost, manhours, and quantity. As said “trend is your friend”, most Project Managers are interested in seeing S-curves in project reports.
S-Curve is a mathematical graph or illustration that properly illustrates the appropriate cumulative data for a project or task. This data can be the cost or man-hours plotted against time.
The reason why it’s called an S curve is not a very technical one. It’s because of the S-shape that the graph makes. The shape, however, depends on the type of project, so other formations are possible.
Some of the most common uses for s-curves are measuring progress, evaluating performance, and making cash-flow forecasts.
Why an “S”?
The S-Curve often forms its shape because the growth of the project in the beginning stages is usually slow. As more progress is made, the growth accelerates rapidly, creating an upward slope that forms the middle part of the “S.”
After the midpoint, the growth begins to plateau, 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.
Banana Curve
Once your baseline S-curve is created, you can play with the inputs to identify the impact on the project.
The most common example is plotting the earliest and latest start dates for tasks in your project schedule. These two S-curves typically overlap at the beginning and end of the project, producing a banana-shaped curve known as “Banana Curves”. The banana shape envelope of the early and late curves represents the range of possibilities that the project can expect if it is completed on time.
Project managers often estimate the earliest, and latest, a task can start in the schedule while not affecting the overall duration. This indicates how much flex or ‘float’ there is in the schedule should things change during project execution.
As actual work is delivered, you can plot this against the banana curve. If the data points are close to the ‘latest date’ curve, it flags the risk of project delay and prompts the project team to take action.
S–Curve helps
- to track the project status
- to make predictions about project progress, performance, cost, resources and quantity
- to prepare you for upcoming risks and opportunities
- to compare baseline vs. current status
Let’s make use of the S curve to predict the project’s future.
Need help? Explore how zerofloat can help you control your project.