Construction PMs and Accountants: Job Cost Variance, Forecast with EAC
Job cost variance is the difference between the value of work actually earned and what it cost to get there, and its sign tells you everything you need to know at a glance: positive means you’re under budget, negative means you’re bleeding money. The core formula, CV = EV - AC, is where every deeper analysis starts.
TL;DR:
- Calculate cost variance for both the current period and the full job, because period figures expose emerging problems while cumulative figures reveal the overall trend.
- Before investigating a variance, check payroll hours, invoice timing, cost code mapping, and overhead allocations; mismatches can create apparent overruns unrelated to project performance.
- Set green, yellow, and red bands at about 5% and 20%, add a dollar floor, and scrutinize unusually favorable results for undercounted work.
- Review EAC monthly using either a fresh estimate to complete plus actual costs, or BAC divided by CPI when current performance is expected to continue.
Table of Contents
- Defining Job Cost Variance and the Numbers Behind It
- Worked Examples: Labor, Materials, and a Full Job
- Setting Thresholds and Running a Focused Variance Analysis
- How EAC and VAC Turn Variance Into a Forecast
- Where to Find the Numbers and How to Check Them First
- Why Disconnected Systems Create Fake Variance
- A Practical First Step This Week
- DesignFlow Build: Fewer False Variances, Faster Forecasts
- FAQ
- Sources
Defining Job Cost Variance and the Numbers Behind It
Cost variance (CV) equals earned value (EV) minus actual cost (AC). EV is the budgeted value of the work you’ve actually completed, not what you planned to complete by now. AC is what you really spent to get there, pulled from payroll, invoices, and your job-cost ledger. Planned value (PV) is the budget for the work you scheduled, used mainly to calculate schedule variance rather than cost variance directly.
Two other terms matter for forecasting: BAC (budget at completion, your total approved budget) and EAC (estimate at completion, your current best guess at final cost). VAC (variance at completion) compares the two.
You can calculate CV for a single period (this month’s labor, say) or cumulatively (the whole job to date). Period figures catch problems fast; cumulative figures show the overall trend. According to AACE’s variance analysis guidance, both views matter, and mismatched data sources, like payroll cutoffs that don’t align with your WIP ledger, are a common reason the numbers look wrong when they’re actually just misaligned.
Worked Examples: Labor, Materials, and a Full Job
Run these on your own numbers before you trust a report.
- Labor rate and efficiency. Say a crew is budgeted at $35 per hour for 400 hours ($14,000), but actually works 420 hours at $37 per hour ($15,540). Rate variance is (budgeted rate minus actual rate) times actual hours: ($35 - $37) x 420 = negative $840. Efficiency variance is (budgeted hours minus actual hours) times budgeted rate: (400 - 420) x $35 = negative $700. Both variances are unfavorable.
- Materials price and usage. Budgeted material cost is 1,000 units at $8 ($8,000); actual is 1,050 units at $8.50 ($8,925). Price variance: ($8 - $8.50) x 1,050 = negative $525. Usage variance: (1,000 - 1,050) x $8 = negative $400.
- Whole-job CV. If EV for the month is $90,000 and AC is $95,000, CV = -$5,000. You’re over budget for the value actually earned.
Before acting on any of these, check for mis-mapped cost codes and timing gaps between when costs hit the ledger and when the related work was actually performed. Those two issues cause more false variances than anything else.
Setting Thresholds and Running a Focused Variance Analysis
Not every variance deserves a meeting. A tiny negative CV on a $2 million job might be noise, while a swing of a few thousand dollars on a $50,000 phase could be a real warning sign. AACE’s recommended practice on variance analysis suggests combining a percentage threshold with a dollar floor, and using stoplight bands to prioritize review.
- Green: variance within roughly 5% of budget, no action needed.
- Yellow: variance between 5% and 20%, worth a quick look.
- Red: variance beyond 20%, or beyond your dollar floor, needs root-cause work now.
An unusually favorable variance deserves scrutiny too: it can mean work was undercounted, not that costs are actually low.
When a variance lands in yellow or red, validate the numbers first, isolate which cost element drove it (labor, material, or an allocation), talk to the site or project manager, update your estimate to complete, and revise EAC following proper incident reporting and corrective action procedures. Project controllers or job-cost accountants typically own this process and escalate to leadership when a red variance threatens the overall budget.
Pro Tip: Check your data source before you chase a root cause. A mismatched invoice date often looks exactly like a real cost overrun.
How EAC and VAC Turn Variance Into a Forecast
Cost variance tells you where you stand today. Estimate at completion (EAC) tells you where you’re headed. Two common formulas, drawn from AACE’s EAC guidance, cover most situations: EAC = AC + ETC, where ETC is a fresh bottoms-up estimate to complete, and EAC = BAC / CPI, which assumes the cost performance you’ve seen so far will hold for the rest of the job.
If BAC is $500,000 and CPI (cost performance index, EV divided by AC) is 0.90, EAC = $500,000 / 0.90, or about $555,556. Variance at completion, VAC = BAC - EAC, would then be roughly negative $55,556: your likely overrun if nothing changes.
The GAO’s guidance on earned value techniques notes that poor EVM implementation correlates with cost overruns on major projects, which is exactly why periodic EAC review matters more than a one-time calculation. TCPI (to-complete performance index) shows the efficiency you’d need going forward to hit BAC or a revised EAC. When CPI trends keep missing that target, it’s time to rebaseline and reopen the VAR.
Where to Find the Numbers and How to Check Them First
A job cost variance report typically shows budgeted or standard cost, actual cost to date, committed cost, and the resulting variance, broken out by cost code. WIP screens roll this up by project and show percent complete alongside billed versus earned revenue.
Before you open a formal variance analysis report, run through this:
- Confirm payroll hours charged to the job match the hours actually worked on it.
- Check that invoice posting dates line up with when the work happened, not when the paperwork cleared.
- Verify indirect costs are allocated to the correct cost codes, not dumped into a catch-all bucket.
AACE’s guidance on accounting considerations in cost control points out that variance reporting is only as good as the mapping between your budget structure and your general ledger codes. Get that mapping wrong and every variance report downstream inherits the error.
Why Disconnected Systems Create Fake Variance
A lot of what looks like job cost variance is actually a reconciliation problem. When payroll lives in one system, invoices in another, and job costing in a spreadsheet, timing mismatches and mapping errors show up as cost swings that have nothing to do with actual project performance.
Consolidating field data, payroll, and job costing into one system removes that noise at the source, because every cost hits the same ledger the moment it happens, under the same cost code, without a manual re-entry step. For teams building out their EVM process, our earned-value construction guide and our job cost dashboard walk through what that looks like in practice.
A Practical First Step This Week
Run cost variance monthly, not quarterly, and investigate anything outside your threshold bands immediately. This week, reconcile payroll and material invoices against your WIP ledger for the current month before trusting any report.
— Keith
DesignFlow Build: Fewer False Variances, Faster Forecasts
Most job cost variance isn’t a performance problem, it’s a data problem: payroll in one tool, invoices in another, job costing patched together in spreadsheets. We built DesignFlow Build as a single construction ERP where field hours, payroll, purchasing, and job costing by cost code live in the same place, so your EV and AC figures come from one source instead of three reconciled ones.
Less manual entry means fewer timing mismatches showing up as phantom variances in your next report.
- Construction ERP combines project management, accounting, and job costing in one system.
- Visit our pricing page for current details on plan costs and seat pricing.
- Implementation typically takes a few weeks, with self-guided options available.
Take a look at our pricing page to see which plan fits your team.
FAQ
How do I calculate cost variance?
Subtract actual cost from earned value: CV = EV - AC. A positive result means the work is costing less than its earned value, a negative result means it’s costing more.
What is an acceptable variance?
Acceptable ranges depend on project size and phase, but AACE’s recommended practice suggests stoplight bands, such as within about 5% as green and beyond 20% as red, combined with a dollar floor so small jobs aren’t flagged for trivial swings.
What is the formula for job costing?
Job costing tracks actual cost by job and cost code against the budgeted or estimated cost for that same scope, and the resulting gap is your cost variance. It relies on accurate labor, material, and overhead allocation to each job.
How is MUV calculated?
Materials usage variance (MUV) is the difference between budgeted and actual quantity used, multiplied by the standard price: (budgeted quantity minus actual quantity) x standard price. A negative result means more material was used than budgeted.
Sources
- 86R-14: Variance Analysis and Reporting (AACE)
- GAO-10-2: Information Technology: Agencies Need to Improve the Implementation and Use of Earned Value Techniques to Help Manage Major System Acquisitions