What Is the S-Curve In Project Management? (2024)

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Published: Jun 7, 2023, 11:00am

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An S-curve is a mathematical graph that shows the progress of a project over time. Its name comes from its “S” shape. While the S-curve starts off slow initially and looks like a straight line, it eventually accelerates as the project gains momentum.

This is when the steep curve upward continues to form in the middle part of the “S.” Once the project is at its peak and heads toward the completion stage, progress slows and the curve levels out again.

Project managers often use an S-curve to track the progress of a project and pinpoint potential issues. An S-curve can also help them compare the actual progress of a project to the planned progress so they understand performance and whether or not any changes need to be made.

There are several types of S-curves, including:

Baseline S-Curve

Before a project starts, most project managers create a schedule that outlines the required resources and sequence of work. This schedule is known as the baseline schedule and the S-curve that comes from it is known as the baseline S-curve. The baseline S-curve shows the expected progress of a project.

Target S-Curve

It’s fairly common for changes to be made to the baseline schedule once a project is in full swing. This altered schedule is called the production schedule and its S-curve is the target S-curve.

While the production schedule starts as the baseline schedule, it usually changes as the project progresses. If a project is completed on time and under budget, it will intersect with the baseline S-curve. However, if it’s delayed and over budget, it will end over and to the right.

Costs vs. Time S-Curve

The costs vs. time S-curve can come in handy for projects that involve labor and non-labor costs, such as hiring, subcontracting and providing materials. It shows the total costs incurred during the project life cycle. It may be used to calculate the overall project costs and cash flow.

Value and Percentage S-Curves

Value S-curves are visual representations of the man-hours or costs that a project has spent so far and the amount required to complete the project. Percentage S-curves compare the completed project against the planned completion in percentage form to reveal the percentage growth and contraction rates.

Man-Hours vs. Time S-Curve

The man-hours vs. time S-curve indicates the amount of manpower and hours put into a project over time. It’s particularly useful for labor-intensive projects.

Actual S-Curve

The production schedule is usually changed frequently throughout the life cycle of a project. These changes include the data from the completed work and can be used to create an actual S-curve, which shows actual progress.

There are a number of benefits of using an S-curve while managing projects, such as:

Track Progress

With an S-curve, you can determine how a project is progressing. In a perfect world, it would progress as planned. However, if a project is behind schedule, you may be able to correlate slowdowns with specific events and then make changes that either prepare for them or avoid them.

Allocate Resources

Once you plot an S-curve, you’ll know when a project will require the most resources. With this information, you’ll find it easier to accurately budget for resources and allocate them properly. It can also convince key stakeholders that you need to supplement your project team with subcontractors, for example.

Forecast Cash Flow

An S-curve can predict the development of cash flow or the cash moving into and out of your business at a specific point in time. With this information, you and key stakeholders will be able to determine cash requirements throughout the project.

Manage Stakeholder Expectations

Not only can an S-curve keep your team members on the same page for project deliverables, it may also engage stakeholders and manage their expectations. You can use it to provide them with a realistic view of a project and its progress.

Find Flexibility

The banana curve is made up of two S-curves that join together: one that shows the earliest start dates for tasks and another one that reveals the latest start dates for tasks. You can use it to find flexibility in the project schedule. Just keep in mind that if progress nears the late S-curve, the project will likely get delayed.

Fortunately, all you need to create an S-curve is an easily accessible tool such as Microsoft Excel or Google Sheets. Once you have it, follow these easy steps.

1. Enter Data

First and foremost, plug in the data you’ll need for your S-curve. Typically, this will include the dates of each project task or milestone as well as the planned and actual progress for each one of them.

2. Select the Data

Drag your mouse over the data to select it. Don’t forget to include column and row headers.

3. Choose the Chart Type

After you select your data, go to the “Charts” panel so you can choose the right one. For an S-curve, you have several options, including: a Scatter with Smooth Lines chart, a 2-D Line chart, a 2-D Line with Markers chart or a 3-D Line chart.

4. Customize Your Chart

Lastly, edit your S-curve so that it meets your needs. You can change its name and colors as well as add any useful information that will help others make sense of the data.