Variance at Completion: Formula, Examples & How to Calculate it?

Variance at completion (VAC) is a key metric in project cost management that helps you forecast whether a project will finish under or over budget. Using the variance-at-completion formula, you can compare the budget at completion (BAC) with the estimate at completion (EAC) to determine the expected financial outcome. 

Variance at completion provides early insight into potential budget issues, allowing teams to take corrective action before the project ends. Understanding variance at completion is essential for PMP candidates and experienced project managers because it improves cost forecasting, supports better decision-making, and strengthens overall project financial control.

What is Variance at Completion (VAC)?

Variance at Completion is a projection of how much a project will run over or under its budget by the time it ends. It is the difference between the budget at completion (BAC) and the estimate at completion (EAC). Put simply, VAC tells you whether you expect to finish with a surplus or a deficit.

• Budget at Completion (BAC): The total approved budget for the entire project.
• Estimate at Completion (EAC): The current forecast of what the project will actually cost when complete.

The VAC formula is straightforward:

VAC = BAC – EAC

If the result is positive, you expect to finish under budget; zero means you plan to hit the budget exactly; a negative number signals a budget overrun.

Why VAC Matters for Project Managers

Statistics paint a sobering picture: a 2025 analysis found that 78% of corporate and public real estate owners in the United States regularly exceed their construction budgets. Only 31% of projects stay within 10% of their original budgets, and just 25% meet their planned timelines. These figures highlight how rare it is to finish on target and underscore the need for early warnings when costs are drifting. VAC provides that warning by comparing what you planned to spend with what you now expect to spend.

Knowing the variance at completion lets you make informed decisions. A positive VAC might allow you to reinvest the savings in additional features, while a negative VAC may require scope adjustments or funding requests. When budgets are tight, having advance notice helps maintain stakeholder trust and prevents surprises.

Key Terms: BAC, EAC, ETC, TCPI, and VAC

In earned value management, several metrics work together to describe cost performance:

• Budget at Completion (BAC): The total approved budget.
• Estimate at Completion (EAC): Updated projection of total cost at finish.
• Estimate to Complete (ETC): Funds still needed to finish the work; it does not include costs already incurred.
• To-Complete Performance Index (TCPI): The cost performance that must be achieved to complete the project within the BAC.
• Variance at Completion (VAC): The expected difference between BAC and EAC.

Understanding these definitions helps you see how VAC fits into the broader picture. It is not a standalone measure but part of a suite of tools for monitoring cost health.

How to Calculate Variance at Completion

The formula for VAC is a simple subtraction:

VAC = BAC – EAC

Imagine that your project has a BAC of $100,000. Halfway through the work, your updated forecast (EAC) suggests the project will cost $95,000. 

Using the formula, VAC = $100,000 – $95,000 = +$5,000. 

The positive number indicates you expect to finish $5,000 under budget. 

Conversely, if the EAC were $110,000, the calculation would yield -$10,000, signaling a $10,000 budget overrun.

Interpreting VAC Results

The value of VAC is more than just a number; it tells a story about your budget.

• Positive VAC (Under Budget): A positive value means you expect to spend less than the approved budget. You could decide to add scope, build contingency, or simply celebrate efficiency. However, treat this projection cautiously; it may change as the project evolves.
• Zero VAC (On Budget): A zero value means your forecast aligns perfectly with the budget. It reflects strong estimating and disciplined execution.
• Negative VAC (Over Budget): A negative value indicates you anticipate spending more than planned. This is a signal to adjust scope, negotiate additional funding, or seek efficiencies. Do not hide or manipulate data; transparency is essential for trust and ethical practice.

Examples of VAC

Now, I will provide two examples of VAC.

Example #1

For your project, the Budget at Completion is 100,000 USD, and the Estimate at Completion is 115,000 USD. Calculate the Variance at Completion given in the question:

BAC = 100,000 USD

EAC = 115,000 USD

We know that

VAC = BAC – EAC

= 100,000 – 115,000

= –15,000 USD

Since the VAC is negative, the project is expected to be over budget by 15,000 USD.

Example #2

For your project, the Budget at Completion is 115,000 USD, and the Estimate at Completion is 100,000 USD. Calculate the Variance at Completion.

Given in the question:

BAC = 115,000 USD

EAC = 100,000 USD

We know that

VAC = BAC – EAC

= 115,000 – 100,000

= 15,000 USD

Since the VAC is positive, the project is expected to be under budget by 15,000 USD.

Common Challenges and Mistakes When Using VAC

Project managers sometimes misinterpret VAC because they forget that it reflects future projections. A few frequent pitfalls include:

• Ignoring changing conditions: Forecasts must be updated regularly. If any scope, schedule, or resource assumptions change, update the EAC and recalculate the VAC.
• Assuming a positive variance is permanent: Early cost underruns can disappear if later phases are more expensive. Use a positive VAC to explore opportunities but maintain a realistic view.
• Focusing solely on cost: VAC does not consider schedule performance. Pair it with metrics like Schedule Variance (SV) and Cost Performance Index (CPI) for a complete picture.
• Poor communication: Stakeholders need clear explanations about what VAC means and what actions it triggers. Provide simple narratives and avoid jargon.

VAC in Context: Related Earned Value Metrics

VAC is part of the family of earned value. To interpret it properly, understand how it connects to other metrics:

• Cost Variance (CV): Measures the difference between earned value (EV) and actual cost (AC) at a specific point in time. Unlike VAC, CV looks at current performance rather than forecasting the final outcome.
• Schedule Variance (SV): Compares earned value and planned value (PV) to show whether the project is ahead of or behind schedule.
• Cost Performance Index (CPI): Ratio of earned value to actual cost; values above 1.0 suggest cost efficiency.
• To-Complete Performance Index (TCPI): Shows the efficiency needed to complete the project within budget or within a revised budget. A TCPI greater than 1.0 indicates a need for improved cost performance.

These metrics complement VAC. For example, a negative VAC combined with a CPI below 1.0 signals both current and future cost problems. Conversely, a positive VAC with an SV greater than zero suggests strong cost and schedule performance.

Best Practices for Managing Budget Variance

Managing budget variance requires more than applying a formula. Consider these best practices:

• Define a realistic budget. Invest time in accurate estimating. Involve key stakeholders to ensure all cost elements are captured.
• Monitor progress frequently. Update your EAC regularly using current performance data. Early detection of deviations allows corrective action.
• Pair cost and schedule metrics. VAC works best alongside CV, SV, and CPI. A complete view improves decision-making.
• Communicate transparently. Share variance information with sponsors and team members in plain language. Explain causes and proposed corrective actions.
• Learn from experience. After project closeout, document lessons learned on budget forecasting and variances. Apply them to future planning.
• Develop financial acumen. Enhance your understanding of business drivers to align project budgets with organizational goals. This leads to higher budget adherence.

FAQs

Q1. How does VAC differ from cost variance (CV)? 

VAC forecasts the final budget difference by comparing BAC and EAC. Cost variance compares earned value and actual cost at a specific point in time. VAC looks ahead; CV looks at the present.

Q2. What does a negative VAC mean? 

A negative value means you expect to exceed the budget at completion. It signals a potential cost overrun and invites corrective actions such as scope adjustments or funding requests.

Q3. Can VAC change during a project? 

Yes. As actual costs and forecasts evolve, the Estimate at Completion will change. Recalculate VAC regularly to ensure it reflects the latest information.

Q4. Is VAC only for PMP exam preparation? 

No. While it is a common exam topic, VAC is a practical tool for real projects. It helps managers anticipate budget issues and communicate them to stakeholders.

Summary

Variance at Completion is a simple yet powerful metric. By subtracting the latest cost forecast from the approved budget, project managers gain an early warning of budget overruns or underspends. When combined with other earned value metrics, VAC supports informed decisions, transparent communication, and better financial control. In an environment where most projects struggle to stay on budget, regularly calculating and acting on VAC can make the difference between success and failure.

Further Reading:

• What is Earned Value Management?
• What are EV, PV, and AC?
• What is SV?
• What is SPI?
• What is CPI?
• What is CV?

This topic is important from a PMP exam point of view.