SPI Calculator
What is a SPI Calculator?
What is SPI?
SPI evaluates time efficiency by measuring the proportion of earned work completed against the scheduled baseline plan.
Formula
Schedule Performance Index (SPI) = Earned Value (EV) ÷ Planned Value (PV)
Variables Explanation
- EV: Earned Value ($).
- PV: Planned Value ($).
How to Calculate
1. Input Earned Value (EV).
2. Input Planned Value (PV).
3. Divide EV by PV.
4. Evaluate efficiency (SPI > 1.0 = Ahead 🟢, SPI < 1.0 = Behind 🔴).
Worked Example
EV = $450,000, PV = $500,000.
SPI = 450,000 ÷ 500,000 = 0.90.
Interpretation: Project is progressing at 90% efficiency relative to baseline schedule (10% behind schedule).
Practical Construction & Project Controls Use
Used in project controls dashboards, S-curve analysis, and progress audit reports.
Understanding the Result
SPI = 1.0 means exactly on schedule. SPI > 1.0 means ahead. SPI < 1.0 means behind schedule.
Limitations & Assumptions
As project reaches completion, SPI trends to 1.0 regardless of delay. Combine with CPM float analysis.
Frequently Asked Questions
What is a good SPI score in project management?
An SPI of 1.0 or higher indicates satisfactory or ahead-of-schedule project performance.
What does an SPI of 0.85 mean?
It means the project is progressing at only 85% of its planned rate, accomplishing 15% less work than scheduled.
Can SPI be calculated using working days?
Standard EVM calculates SPI using currency values (EV/PV), but schedule progress % can provide equivalent estimates.
How does SPI differ from SV?
SPI is a relative efficiency ratio (EV/PV), while SV is an absolute dollar difference (EV - PV).
Why does SPI lose forecasting accuracy near project completion?
Because EV approaches PV as final work finishes, forcing SPI back toward 1.0.