# CPI and SPI worked examples: read both sides of performance

Practice CPI and SPI with three original worked examples, clear cost and schedule interpretations, and the checks needed before reporting project health.

Source: https://tirtle.com/blog/cpi-spi-worked-examples
Publisher: Tirtle | Updated: 2026-10-10

## The short answer

CPI measures cost efficiency as EV / AC. SPI compares accomplished work with planned work as EV / PV. Read them separately before combining the story. A project can be cost-efficient while behind its plan, or progressing ahead of its plan while spending inefficiently.

## Label the numbers before dividing

Use EV, the budgeted value of accomplished work, as the numerator for both calculations. The denominator determines the question. Actual cost asks how much the accomplishment cost. Planned value asks how the accomplishment compares with the work scheduled by this date.

All the examples below use original teaching numbers at a shared reporting cutoff. They assume the earning rules and cost records are reliable. That matters because correct arithmetic on incomplete actuals or exaggerated progress still produces a misleading report. Write the labels beside the inputs before reaching for a calculator.

## Example one: under cost, behind plan

A training material project reports PV = $30,000, EV = $24,000, and AC = $20,000. CPI is $24,000 / $20,000 = 1.20. SPI is $24,000 / $30,000 = 0.80.

The accomplishment cost less than its assigned budget, but the team has accomplished less budgeted work than planned. Saying the project is under budget and therefore healthy misses the schedule comparison. Ask whether the unfinished modules affect a required training date and whether the cost result reflects a durable efficiency or a temporary reporting effect.

## Example two: over cost, ahead of plan

A warehouse labeling project reports PV = $40,000, EV = $48,000, and AC = $60,000. CPI is 0.80. SPI is 1.20. The team has accomplished more budgeted work than scheduled, while the actual cost exceeds the budgeted value of that accomplishment.

Perhaps overtime accelerated installation, but the indices cannot prove that cause. Check work records and the reason for the spending before recommending a change. Finishing early can be useful, yet the extra cost may or may not be justified by the benefit. That needs a business decision rather than a color on a dashboard.

## Example three: both indices below one

A reception redesign reports PV = $50,000, EV = $40,000, and AC = $50,000. CPI is 0.80 and SPI is 0.80. Both comparisons are unfavorable. CV is -$10,000 and SV is also -$10,000, although the matching amounts describe different things.

You still cannot conclude that the finish will be exactly 20% late. SPI uses budgeted work, not elapsed days. Review the remaining schedule and critical dependencies. You also need to assess whether current cost efficiency will continue before selecting an estimate-at-completion formula.

## Turn the result into a useful update

Use a plain statement that separates the measurement from the explanation. For example: cost efficiency is unfavorable, and accomplished work is below plan; the team is investigating rework in the reception drawings before recommending a recovery action.

Then check the following before distributing the update.

- Do PV, EV, and AC use the same reporting date and scope?
- Is earned progress supported by the agreed measurement rule?
- Have incurred costs been captured, including relevant accruals?
- Is the trend different from the previous reporting period?
- Which decision or investigation follows from the result?

## Your next step

CPI and SPI answer different questions. Read both accurately, then use evidence from the work to explain the cause and choose a response.

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## Sources

- [Earned value management](https://www.pmi.org/blog/earned-value-management) | Project Management Institute

## Keep learning

- [Earned value management formulas, explained with one example](https://tirtle.com/blog/earned-value-management-formulas)
- [Estimate at completion formulas: choose the assumption first](https://tirtle.com/blog/estimate-at-completion-formulas)
- [A critical path method example you can work through](https://tirtle.com/blog/critical-path-method-example)

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