Schedule variance is a project management metric that measures the difference between a project's planned and actual progress at a given time. It is an essential metric for project cost and progress analysis, helping managers understand exactly how their project performs and whether it is in jeopardy of being delayed.
Understanding Schedule Variance
In project management, particularly within the framework of Earned Value Management (EVM), schedule variance (SV) quantifies how much a project is ahead of or behind its planned schedule. It compares the value of the work actually completed to the value of the work planned to be completed by a specific point in time.
Think of it this way: If you planned to have finished building a certain portion of a structure by today, schedule variance tells you if you have actually finished more, less, or exactly that amount of work by today.
How Schedule Variance is Calculated
Schedule variance is calculated using a simple formula derived from Earned Value Management principles:
SV = Earned Value (EV) - Planned Value (PV)
- Planned Value (PV): The authorized budget planned to be spent on the work scheduled to be completed by a specific date.
- Earned Value (EV): The authorized budget for the work actually completed by a specific date.
Both EV and PV are typically expressed in a currency unit (like dollars) or other standard units of measure, reflecting the value of the work rather than just hours or physical units.
Interpreting Schedule Variance
The result of the SV calculation provides a clear indicator of the project's schedule performance:
| Schedule Variance (SV) | Interpretation | Project Status |
|---|---|---|
| SV > 0 (Positive) | You have completed more work than planned. | Ahead of schedule. |
| SV < 0 (Negative) | You have completed less work than planned. | Behind schedule. |
| SV = 0 (Zero) | You have completed exactly the amount of work planned. | Exactly on schedule. |
As the reference notes, a negative schedule variance indicates that the project may be in jeopardy of being delayed.
Practical Insights and Solutions
Monitoring schedule variance is crucial for proactive project management. Here are some practical insights based on SV results:
- If SV is Positive:
- The project is ahead of schedule. This is generally positive, but investigate why. Is the estimate inaccurate? Were resources more efficient than expected?
- Action: Maintain momentum, potentially reallocate resources to critical path tasks if needed, or use the buffer for future potential issues.
- If SV is Negative:
- The project is behind schedule and potentially faces delays.
- Actions:
- Identify the specific tasks causing the delay.
- Determine the root cause (e.g., resource issues, scope creep, unexpected problems, poor estimates).
- Implement corrective actions such as adding resources, crashing the schedule (adding resources to speed up critical tasks), fast-tracking (doing tasks in parallel), or renegotiating scope or deadlines if necessary.
- Update the project schedule and communicate the impact to stakeholders.
- If SV is Zero:
- The project is exactly on schedule in terms of the value of work completed. Continue monitoring closely to ensure this remains the case.
Schedule variance is a lagging indicator, meaning it tells you about past performance. To manage effectively, it's important to use it in conjunction with other metrics and forecasts to predict future performance and take timely action.
