SPI Calculator
Calculate SPI step by step: SPI = EV ÷ PV.
In short
Formula: SPI = EV ÷ PV.
What this calculator does
Calculate SPI step by step: SPI = EV ÷ PV. Worked example, questions and limitations included.
Use it to turn Earned value (EV), Planned value (PV) into a checked result you can compare, copy, or rerun with different assumptions.
The page shows the formula, a numeric worked example, and the assumptions that affect this earned value calculation.
Inputs and what they mean
- Earned value (EV)
- — number value.
- Planned value (PV)
- — number value.
How to use it
- Enter each value in the unit shown next to the box (use the unit converter first if your numbers are in other units).
- Check the breakdown to see every intermediate step.
- Read the limitations before relying on the result.
Formula
Definitions follow the PMI PMBOK Guide and the ANSI/EIA-748 earned value management standard.
SPI below 1 means less work has been done than planned by this date.
Planned value must be above zero; early in a project the index is unstable.
SPI = EV ÷ PV.
Inputs used: Earned value (EV), Planned value (PV).
Worked example
EV 175,000, PV 200,000
- SPI = 175,000 ÷ 200,000 = 0.875.
Reading the result
The headline figure is the main answer. Any breakdown underneath shows the parts that make it up, so you can check the working and see what changes when you adjust an input.
Limitations and assumptions
- A single cumulative index hides which work is late or over budget.
- Ignores the critical path.
- Unstable early in the project when values are small.
- Results are planning estimates built only from the figures you enter. They are not a guarantee of cost, schedule or delivery, and they do not replace your organisation's own project controls.
- The result depends on the values you enter for this spi calculator; it does not supply missing rates, rules, prices, dates, or assumptions for you.
Common questions
Why does SPI drift to 1 at the end?
Because EV and PV both reach BAC at completion. Late projects therefore show SPI = 1 at finish. Earned schedule methods address this.
Does SPI tell me the finish date?
Only roughly: planned duration ÷ SPI is a common first estimate. Use the schedule forecast calculator for that.
Can SPI be above 1 while critical tasks are late?
Yes. SPI averages across all work, so non-critical work done early can hide a late critical path.
How do I use the SPI Calculator?
Enter the required values for Earned value (EV), Planned value (PV). The calculator applies the formula on this page and shows the main result with any supporting breakdown so you can check the arithmetic.
What formula does the SPI Calculator use?
SPI = EV ÷ PV. The visible formula section above lists the calculation path and the edge cases the page handles, so the result can be checked without relying on the form alone.
Can the SPI Calculator be used for exact decisions?
Use it as a calculation aid, not as a substitute for checking the underlying rule, contract, policy, or professional advice that applies to your situation. When a result depends on local rules, personal details, prices, or dates, enter those values yourself and confirm them before acting.
Related tools
Calculate Planned Value step by step: PV = BAC × planned % complete at the status date.
Calculate Earned Value step by step: EV = BAC × actual % complete.
Calculate Actual Cost (Earned Value) step by step: AC = sum of all costs actually incurred for the work performed to the status date.
Calculate Budget At Completion step by step: BAC = sum of the budgets of all work packages in the performance measurement baseline.