Project Management guide · Cost and resources
Schedule Variance (SV): Formula, Examples and Limitations
Schedule variance (SV) measures whether a project has completed more or less work than planned by a given date, expressed in money. It is calculated as SV = EV - PV; a negative result means the project is behind schedule.
Key takeaways
- SV = EV - PV; negative means behind schedule.
- SV is in money and returns to zero at completion.
- Check the critical path, not just SV, before drawing conclusions.
- Earned schedule converts SV into time units.
The formula
| Formula | Meaning |
|---|---|
| SV = EV - PV | Schedule variance in money |
| SV% = SV / PV | Schedule variance as a percentage of planned work |
| SPI = EV / PV | Schedule performance index |
| Result | Meaning |
|---|---|
| SV > 0 | Ahead of schedule |
| SV = 0 | On schedule |
| SV < 0 | Behind schedule |
Worked example
At month four PV = $80,000 and EV = $70,000.
- SV = 70,000 - 80,000 = -$10,000.
- SV% = -10,000 / 80,000 = -12.5%.
- SPI = 70,000 / 80,000 = 0.875: the team has achieved 87.5% of the work planned by now.
Limitations of SV
- It is in money, not time. -$10,000 does not tell you how many days late you are.
- It returns to zero at the end. When all work is done, EV = PV = BAC, so SV = 0 even if the project finished months late.
- It ignores the critical path. Work done ahead of plan on non-critical tasks can hide delays on critical ones; see critical path method.
Earned schedule: SV in time units
Earned schedule (ES) finds the point in time when the current EV should have been earned. Using the cumulative PV of $50,000 at month three and $80,000 at month four, an EV of $70,000 was planned at:
- ES = 3 + (70,000 - 50,000) / (80,000 - 50,000) = 3 + 0.67 = 3.67 months.
- Actual time (AT) = 4 months, so SV(t) = 3.67 - 4 = -0.33 months (about a third of a month behind).
- SPI(t) = 3.67 / 4 = 0.92.
What to do about negative SV
- Check whether delayed work is on the critical path.
- Find the cause: resources, dependencies, scope, supplier delays.
- Consider schedule compression: fast-tracking or crashing.
- Re-sequence or reassign work using resource leveling.
- Update the forecast completion date and inform stakeholders.
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Frequently asked questions
What is schedule variance?
The difference between earned value and planned value, SV = EV - PV, showing whether more or less work has been done than planned.
What does a negative schedule variance mean?
Less work has been completed than planned by this date, so the project is behind schedule.
Why is schedule variance measured in money?
Because earned value measures work in budget terms. Earned schedule converts it into time.
How do you calculate SV percentage?
SV% = SV / PV x 100. For SV of -$10,000 and PV of $80,000 it is -12.5%.
Why does SV become zero at the end of a project?
When all work is complete, EV equals BAC and so does PV, so SV is zero regardless of lateness.
What is the difference between SV and SPI?
SV is the difference (EV - PV) in money; SPI is the ratio (EV / PV).
Can a project have a positive SV and still be late?
Yes, if extra work is being done on non-critical tasks while critical-path tasks slip.
How does earned schedule improve on schedule variance?
Earned schedule is an extension of EVM that measures schedule performance in time rather than money, by finding when the current EV was planned to be earned. Unlike SV, it does not drift back to zero as the project nears completion.
How is schedule variance different from cost variance?
SV = EV - PV compares work done with work planned. CV = EV - AC compares work done with what it cost.
How do you fix a negative schedule variance?
Focus on the critical path, remove blockers, and consider fast-tracking, crashing or re-planning, then update forecasts.