PMP CPI and SPI Questions: Calculate the Number, Then Explain It

You calculate CPI correctly. You calculate SPI correctly. Then the question asks what the numbers mean, and suddenly the calculator looks less helpful.

PMP CPI and SPI questions test interpretation as well as arithmetic. A useful practice routine is to calculate the ratio, describe what it compares, and identify what it cannot tell you.

Keep the three inputs separate

• Planned value (PV): the budgeted value of work scheduled by the reporting point.
• Earned value (EV): the budgeted value of work actually accomplished.
• Actual cost (AC): the cost incurred for the work performed.

Earned value is not the cash received from a customer or the project's expected commercial benefit. Mixing those meanings can derail an otherwise simple calculation.

The PMI overview of earned value management explains these measures and their performance ratios.

Work through this example

At a reporting date, a project has PV of $90,000, EV of $80,000 and AC of $100,000. Use the same reporting point and consistent units for all three inputs.

• CPI = EV / AC = 80,000 / 100,000 = 0.80.
• SPI = EV / PV = 80,000 / 90,000 = approximately 0.89.

CPI below 1 indicates unfavorable cost performance: the project has earned $0.80 of budgeted work value for every $1 spent. SPI below 1 indicates that less budgeted work value has been accomplished than planned at this point.

In ordinary exam language, this is over budget for the work performed and behind schedule in earned-value terms. It does not mean the entire approved project budget has already been spent.

Do not turn the ratio into a claim it cannot support

An SPI of 0.89 does not prove that the project will finish exactly 11% late. The measure compares work value, not a direct count of calendar days. The completion date also depends on the remaining work, sequencing, critical path and corrective actions.

Likewise, CPI of 0.80 does not by itself identify the cause. Rework, estimating problems, resource costs or other factors may contribute. A number can point you toward a conversation; it cannot attend the conversation for you.

Choose a management response that fits the question

If a scenario asks for interpretation, interpret the measures. If it asks what to do next, examine whether the cause has already been investigated. Validate the data, understand the drivers and evaluate responses with the relevant people. Do not automatically replace team members or rewrite the baseline to make a dashboard green.

If the question provides a forecasting assumption, use the formula appropriate to that assumption. Do not treat one forecast method as a universal rule for every project.

A quick self-check before selecting an answer

1. Did I use earned value in the numerator of both ratios?
2. Did I compare cost with actual cost and schedule with planned value?
3. Did I describe performance without inventing a precise completion date?
4. Did I answer the question asked, rather than the one I expected?

Register for the free 25-question PMP practice exam and practice making decisions in a 30-minute session. Review the reasoning behind your answers afterwards. One short result should guide your next study step, not serve as a pass guarantee.

Continue your PMP preparation

Connect performance measures with outcomes in our PMP business value questions guide.

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Written by Sabri Calisici, project management instructor since 2008.