Calculator Form
Large screens use three columns, smaller screens use two, and mobile uses one column.
Example Data Table
| Project | PV | EV | AC | BAC | SPI | Status |
|---|---|---|---|---|---|---|
| Tower Block A | $250,000 | $230,000 | $240,000 | $500,000 | 0.92 | Behind schedule |
| Road Link B | $420,000 | $445,000 | $430,000 | $800,000 | 1.06 | Ahead of schedule |
| Bridge Package C | $310,000 | $310,000 | $300,000 | $620,000 | 1.00 | Near schedule baseline |
Formula Used
SPI = Earned Value (EV) ÷ Planned Value (PV)
SV = Earned Value (EV) − Planned Value (PV)
Forecast Duration = Original Duration ÷ SPI
Planned Progress = PV ÷ BAC × 100
Earned Progress = EV ÷ BAC × 100
An SPI above 1.00 usually means work is progressing faster than planned. An SPI below 1.00 usually means the project is slipping behind schedule.
How to Use This Calculator
- Enter the project name for easy result labeling.
- Add Planned Value and Earned Value. These are required.
- Optionally add Actual Cost and Budget at Completion for extra context.
- Optionally enter original and elapsed duration to forecast total time.
- Select a currency symbol, time unit, and decimal precision.
- Press Calculate SPI to show the results above the form.
- Review the Plotly graph, variance, status, and progress metrics.
- Export the results using the CSV or PDF buttons.
Frequently Asked Questions
1. What is schedule performance index in construction?
Schedule performance index compares earned value with planned value. It shows whether a project is progressing faster, slower, or close to the approved schedule baseline.
2. What does an SPI above 1.00 mean?
An SPI above 1.00 usually means the project is ahead of schedule. The team has earned more value than was planned for the same reporting period.
3. What does an SPI below 1.00 mean?
An SPI below 1.00 usually means the project is behind schedule. The completed work value is lower than the work value that was originally planned.
4. Can SPI be used without actual cost?
Yes. SPI only needs earned value and planned value. Actual cost is not required for SPI, though it helps when reviewing cost performance beside schedule performance.
5. Why is planned value important here?
Planned value represents the authorized budgeted work scheduled for the reporting date. Without it, you cannot compare actual progress against the project plan properly.
6. How often should I calculate SPI?
Most construction teams review SPI weekly or monthly. The best reporting frequency depends on project size, contract controls, stakeholder expectations, and update discipline.
7. Is SPI enough to judge overall project health?
No. SPI is helpful, but it should be reviewed with schedule variance, cost metrics, risk status, productivity trends, and field progress notes for a fuller picture.
8. How is forecast duration estimated from SPI?
A simple schedule forecast divides original duration by SPI. This gives a quick estimate of likely total duration if the current schedule efficiency continues.