All About the Schedule Performance Index in Project Management (SPI)

The schedule performance index is a metric in project management that helps project managers monitor project timelines and efficiency.

SPI works by comparing work completed (known as earned value) and work planned (known as planner value).

The result is an index which can be under, over, or equal to 1, in case of perfectly balanced timelines.

SPI is part of earned value management, a comprehensive methodology which analyzes three project performance factors: schedule, cost, and scope.

Here’s the schedule performance index formula:

work completed (EV) / work planned (PV) = schedule performance index

It’s a simple formula, but you’ll need to calculate two other metrics to get your result:

EV represents the value of all completed work at any given point in your project timeline.

To calculate it, you’ll be using the following formula:
percentage of work completed x original budget of the project = earned value

So, if your project budget is $15,000, and you’ve completed 20% of your work, EV amounts to 0.20 x 15,000 = $3,000.

Having a software system that can help you manage your project progress is valuable for calculating metrics in project management. With Productive, you can track billable hours against your budgets and see profitability and revenue in real time.

The formula for planned value is very similar to EV. But, instead of percentage of work completed, you’ll need the percentage of work that you were planning to complete by a certain point in time.

Here’s the planned value formula:

percentage of work scheduled for completion x original budget = planned value

So, if you scheduled 25% of work to be completed at that time, that means that your PV is 0.25 x $15,000 = $3,750.

Project managers can use Gantt charts and other techniques in the project planning phase in order to create a schedule baseline for their project, which can then be used for these types of analyses.

Now that we have all of the necessary components, we can go back to calculating our schedule performance index.

The SPI is:

3,000 / 3,750 = 0.8

Here are some example calculations to show you the full range of schedule performance index values:

Now that you know the basics, you’re probably wondering how the schedule performance index is used in practice.

Since it’s used in various types of industries, from the construction industry to professional services, a one-size-fits-all external benchmark doesn’t really exist.

However, it can be very useful as an internal benchmark.

By analyzing SPI patterns and applying these findings to future projects, project managers can gather reliable insights for predicting future outcomes and making data-driven decisions.

For example, you can try to detect:

These are just a couple of examples that can help you get the most out of your performance metrics.

According to research on the construction industry by R.B. dos Santos and A. E. Jungles, it was found that the SPI of projects with schedule delays is significantly different from that of projects that are delivered on time.

This means that the schedule performance index can be a great tool for calculating your risk management—consider incorporating it into your risk register.

On the other hand, another research by S. Kim on construction projects showed that SPI had a high chance of deviations from its baseline index of 1.0 throughout a project’s lifetime.

In comparison, successful projects showed a relatively stable CPI. This suggests that, while SPI is useful for tracking schedule performance, it might not be the best sole indicator of project success.

Combining SPI with other metrics provides a comprehensive view of a project’s overall health, helping project managers make more informed decisions and mitigate risks effectively.

Here’s a quick comparison of project management metrics:

Schedule variance is a closely related metric to SPI, as they both take schedule adherence into account, but approach it from different angles.

Schedule variance is calculated by subtracting earned value from planned value. Instead of an index in the SPI formula, the result of SV is a value expressed in cost (money) terms.

So, if your earned value at a point in time is $5,000, and your planned value is $6,000, that means you’re at a -$1,000 loss.

When to use them:

The cost performance index (CPI) calculation is related to SPI, but focuses on cost metrics.

CPI is calculated by dividing earned value by actual cost (AC). This is the sum of all expenses and costs incurred by a particular point in time.

So, if your EV is $5,000 and your AC is $6,000, that means your CPI is 0.83, indicating you’re overspending.

CPI and CV have the same relationship as SPI and SV. Check out our article on cost variance in project management for more information.

When to use them:

You’ll need to calculate your SPI at regular checkpoints, ideally integrating these measurements with your project management software for real-time tracking and analysis.

Here are some important checkpoints for ensuring that you’re tracking the actual progress that project teams are making:

Tracking SPI at these checkpoints allows you to forecast completion dates more accurately and implement corrective measures before minor schedule variances become major delays.

Here are three useful tips and project management techniques that you can use for supporting actual performance:

SPI is an essential metric in the project management toolkit, helping project teams stay on track and within budget.

With project management software such as Productive, you can manage all aspects of your business performance.

First, organize your project within Productive’s Gantt, Workload, Kanban, or other view to visualize your projects. Then, break up larger milestones into tasks and track time against them to manage your billable time.

Within Productive’s Budgeting and Profitability charts, you can view your finances in real time. Productive includes overhead management and expense tracking for more accurate insights.

Finally, Productive also includes resource planning for allocating resources based on capacity and availability. With the Scenario Builder, you can model different scenarios to make data-driven decisions for the future.

Book a demo with Productive to learn more about its benefits for professional services businesses.