Job Cost Variance Calculator for Construction Companies

What Is Job Cost Variance?

Job cost variance tells you whether a job is running over or under budget, and by how much. It is one of the most important numbers a contractor can track during and after a project. Without it, you are managing by gut feel rather than by data.

Most contractors know when a job goes bad eventually. The ones who catch it early enough to do something about it are tracking variance in real time, by cost category, not just as a single total at the end.

The Formula

Job Cost Variance = Budgeted Cost - Actual Cost

A positive result means you are under budget. A negative result means you are over. Tracking variance as a percentage of the original budget makes it easier to compare performance across jobs of different sizes.

Variance % = (Budgeted Cost - Actual Cost) / Budgeted Cost x 100

Why Cost Categories Matter

A single total variance number tells you that something is wrong but not where. Breaking variance down by category tells you exactly where the problem is, which determines what you do about it.

A labor overrun usually points to productivity problems, scope creep, or estimating errors on crew size and hours. A materials overrun often traces back to waste, theft, price changes, or quantity takeoff errors. A subcontractor overrun may signal change orders that were not captured or a sub that bid low and is now claiming extras.

Each category has a different cause and a different fix. Knowing which one is driving your variance is the difference between solving the problem and guessing at it.

A Worked Example

A roofing contractor is tracking a $420,000 commercial re-roof midway through the project:

The job is tracking well overall, but the subcontractor line is over budget. That warrants a conversation with the sub now, not at the end of the job.