Schedule Performance Index Formula and Example - Cost Performance Index Formula and Example

Schedule Performance Index and Cost Performance Index

Schedule Performance Index (SPI) and Cost Performance Index (CPI) allow you to evaluate the performance of a project. They demonstrate the schedule and cost efficiency of a project. Basically, Schedule Performance Index (SPI) can be calculated by dividing the Earned value (EV) by the Planned value (PV). And the Cost Performance Index (CPI) can be calculated by dividing the Earned value (EV) by the Actual Cost (AC). These calculations show how efficiently you are proceeding compared to the planned project work schedule and budget. In this article, we will review Schedule and Cost Performance Index Formulas and Examples.

Schedule Performance Index (SPI)

SPI is a measurement of the productivity of your project depending on the planned work schedule. The ratio of earned value to planned value gives the Schedule Performance Index (SPI). It provides information about the schedule efficiency of the project.

Schedule Performance Index Formula

The  SPI can be calculated by dividing Earned Value (EV) by Planned Value (PV) as shown below.



SPI = EV / PV

The Schedule Performance Index formula gives 3 results regarding the schedule performance of a project.

• SPI > 1: We are ahead of schedule and we completed more than we planned.
• SPI < 1: We are behind schedule. We completed less than we planned.
• SPI =1: We are on schedule. Work is completed as per the planned.

Note that while calculating the SPI of the overall work schedule, be sure that you take for all the activities. Considering only the critical path activities cannot give accurate results. Therefore you must take all the activities.

Schedule Performance Index Example

We have a project to be completed in 30 months and the budget of the project is 100,000,000 USD. 12 months have passed and 45,000,000 USD has been spent, but only 25% of the work has been completed

Now we will calculate the Schedule Performance Index (SPI) and Schedule Variance (SV) based on the information.

Schedule Performance Index (SPI)

Planned Value (PV) = (12/30) x 100,000,000 USD = 40,000,000 USD
Earned Value (EV) = %25 x 100,000,000 USD = 25,000,000 USD
SPI = EV / PV
SPI = 25,000,000 / 40,000,000 = 0,625

SPI < 1 ; The result is less than one . So that we are behind the schedule.

Schedule Variance

SV = EV – PV
SV = 25,000,000 USD – 40,000,000 USD = – 15,000,000 USD

Cost Performance Index



The Cost Performance Index (CPI) is a measurement of your efficiency depending on the Earned Value (EV) and Actual Costs (AC). It is the ratio of Earned value (EV) to Actual Costs (AC). It provides information about the cost efficiency of the project.

The CPI calculates the value of the work completed compared to the actual cost spent.

Simply we can say that The Cost Performance Index (CPI) calculates how much we are earning for each dollar spent on the project.

  • Cost Performance Index Formula

The Cost Performance Index formula gives 3 results regarding to the cost performance of a project.

CPI = EV / AC
• CPI > 1: We are under budget. We are spending less than we earn.
• CPI < 1: We are over budget. We are spending more than we earn.
• CPI =1: We are on budget. We are proceeding as per the planned. If we proceed with this ratio we will complete the project on time.

Cost Performance Index Example

Up to this section, we reviewed the Schedule Performance Index Formula and Example. Now we will analyze a CPI Example for better understanding.



We have a project to be completed in 30 months and the budget of the project is 100,000,000 USD. 12 months have passed and 45,000,000 USD has been spent, but only 25% of the work has been completed

Now we will calculate the CPI and Cost Variance

Cost Performance Index (CPI)

Actual Cost (AC) = 45,000,000 USD
Earned Value (EV) = %25 x 100,000,000 USD = 25,000,000 USD
CPI = EV / AC
CPI = 25,000,000 / 45,000,000 = 0,555

CPI < 1 ; We are over budget. This means that we are earning 0.55 USD for every 1 USD spent.

Cost Variance (CV)

CV = EV – AC
CV = 25,000,000 USD – 45,000,000 USD = – 20,000,000 USD

Keystones



  • A high or low value of SPI or CPI shows that your estimates are not compatible with the targets of your project. You must revise your assumptions and take corrective actions if needed.
  • Both Cost Performance Index (CPI) and  SPI gives 3 results regarding the performance of the project.
  • If the Cost Performance Index (CPI) or  SPI is equal to one, this means that the project is proceeding as per the planned.
  • Both Cost Performance Index (CPI) and Schedule Performance Index (SPI) need Earned Value (EV) to make calculation.
  • Both Cost Performance Index (CPI) and Schedule Performance Index (SPI) measurements depend on the project’s past performance and they can be used to estimate the future performance.
  • Cost Performance Index (CPI) and Schedule Performance Index (SPI) measurements improve decision making among the project team.

Summary



The Schedule Performance Index (SPI), Cost Performance Index (CPI), Schedule Variance (SV) and Cost Variance (CV) are performance indicators used in the Earned Value Management. By the help of these tools, it is easy to understand the health or sickness of our projects. Project size, duration, and other properties do not make any difference in the calculation of these indexes. Project teams must be aware of their project’s current performance to make realistic forecasts for future performance. These metrics provide valuable information that helps to complete a project within budget and approved schedule.

Earned value (EV) measurements use indicators to analyze a project’s past performance and estimate it’s future performance. In this article, we review both the Schedule Performance Index and Cost Performance Index Formulas and Examples. If you are preparing to take the CAPM or PMP Certification Exam, you must know their key aspects and importance for project management.

See Also

Earned Value Management Example

Cost Benefit Analysis Example

External Reference

Earned value

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