Every mining contract has a budget and a schedule. By the time month-end accounting catches a cost problem, the damage is already done. A contractor three weeks into a six-week excavation job needs to know today whether spending is ahead of production or behind it.
One equation answers that question: cost variance equals actual cost to date minus the product of total budget and percent complete. A positive result means you have spent more than the work done justifies. Run it each Friday from your daily field reports and you have the signal you need before the next shift plan is written.
The challenge is not the arithmetic. It is building the three inputs reliably from shift tickets and hourly records already sitting in your field system, so the weekly number is ready in minutes rather than half a day.
The equation: Cost Variance
CV = ACD - (B x PC)Where:
CV- cost variance ($)ACD- actual cost to date, covering all labor, equipment, materials, and subcontractors ($)B- total fixed contract budget ($)PC- percent complete, measured from physical production units rather than from cost (decimal (0 to 1))
Valid for: Holds on fixed-price contracts where percent complete is measured from physical production rather than from cost; not applicable to time-and-materials work where no fixed budget exists.
Source: Form derived from project control principles in SME Mining Reference Handbook, 2nd edition, CHAPTER 9: Project Evaluation, p. 245
Worked example
A surface earthmoving contractor is three weeks into a fixed-price contract for $480,000. Daily shift tickets show $145,000 in total costs across labor, equipment, fuel, and consumables. Field measurements at the end of week 3 show 25 percent of the contracted earthworks volume is complete.
| Step | Calculation | Result |
|---|---|---|
| Convert percent complete to a decimal | 25% = 0.25 | 0.25 |
| Calculate earned value (budget times percent complete) | $480,000 x 0.25 = $120,000 | $120,000 |
| Calculate cost variance | $145,000 - $120,000 = $25,000 | +$25,000 |
Answer: The cost variance at week 3 is +$25,000, meaning the contractor has spent $25,000 more than the value of work completed to date justifies.
What the weekly job cost report must include
A report that shows only a total spend figure is not a management tool. It tells you what you spent; it does not tell you whether that spending was earned. Seven line items give a contractor the full picture each week:
1. Labor hours by crew and shift - actual hours worked, not scheduled 2. Labor cost to date - wages plus payroll burden, stacked from shift one 3. Equipment hours by unit - productive hours from the operator log 4. Equipment cost to date - ownership cost or rental rate multiplied by hours 5. Materials and consumables - fuel, explosives, ground support, drill bits 6. Subcontractor costs - any scope performed by others under your contract 7. Percent complete - based on a physical production measure, not cost
The first six come directly from daily field reports. The seventh requires a separate measurement, and that measurement is where most weekly reports fall apart. A percent complete figure calculated from cost is circular: if you overspend, the formula shows you further along than you are, and the overrun disappears from view.
Use a physical measure: tons hauled, cubic meters excavated, meters drilled, or structures completed. Divide the cumulative quantity by the total contracted quantity. That number goes into the formula, and the formula gives you a variance you can act on.
The SME Mining Reference Handbook (2nd edition, Chapter 9: Project Evaluation, p. 245) identifies a project control system as a required element of both prefeasibility and feasibility-level project work, noting that the system must be outlined before detailed engineering begins. A contractor who sets up cost tracking before the first shift has the structure in place when the numbers start to move.
From daily field reports to a weekly total
The data for a weekly variance calculation already exists in your field reports. The stacking process is mechanical: total each cost line across the week's shifts and you have the input.
Each shift ticket should record:
- Crew names and hours worked by trade or category
- Equipment unit numbers and hours operated
- Fuel issued by unit number
- Materials consumed that shift: bits, consumables, ground support, explosives
- Production achieved: tons moved, meters drilled, or units completed
At the end of the week, total each column. Labor cost is total hours multiplied by the loaded wage rate for each crew category. Equipment cost is total hours multiplied by the ownership or rental rate per hour for each unit. Materials sum directly from daily issues.
Under 30 CFR Part 50, mine operators are required to maintain records of employment and hours worked at the mine site. The same daily field ticket that documents hours per person and shift feeds both the MSHA record and the labor cost line in the weekly job cost total. A shift ticket built to satisfy the regulatory record also satisfies the cost system, with no double-entry required.
The SME Mining Reference Handbook (1st edition, Reporting, p. 389) identifies personnel and equipment utilization, costs, and repair history as the core records a mining maintenance program must keep. That same data set feeds a weekly cost variance calculation when it is captured daily and totaled at week-end.
One cross-check catches most data errors before they compound: equipment hours from the operator log and fuel consumption from the fuel log must be consistent by unit. If a loader shows 9.5 hours on the operator sheet but the fuel issue record suggests roughly 2 hours of operation at that machine's typical consumption rate, one of those numbers is wrong. Catch the mismatch on Friday, not at month-end when the invoice is already out.
Measuring percent complete without a formal survey
You do not need a licensed surveyor to get a usable percent complete figure each week. You need consistent field measurements and a clear definition of the unit you are tracking.
For earthmoving: count loads and multiply by average payload. If you are running 22-ton loads and completed 210 loads over three weeks, that is 4,620 tons. Divide by the total contracted quantity and you have the running percent complete.
For drilling: meters drilled per shift are already on the shift card. Divide cumulative meters by total contracted meters.
For concrete or structural work: count completed bays, installed support sets, or poured sections, depending on what the contract uses as its billing milestone.
The only rule is that the measurement must come from a physical count or production log, not from cost. If you use cost to calculate percent complete and then subtract cost from the result, the formula returns near zero regardless of what is happening on the ground. Progress and cost must be measured independently for the variance to mean anything.
For contracts where scope is difficult to subdivide uniformly (portal development, shaft sinking in variable ground), break the contract into phases and apply the formula to each phase separately. A variance figure for a single phase with consistent conditions is more useful than an aggregate number that mixes easy ground with hard.
The weekly cycle: when the numbers must land
The report means nothing if it is read on Tuesday for the previous week and the shift plan for the coming week was written on Sunday. The timing of the pull is as important as the accuracy of the inputs.
A practical cycle for most contracting operations:
- Friday end-of-shift: supervisors submit final shift tickets and production logs
- Friday evening or Saturday morning: totals are stacked and the variance is calculated
- Sunday before the shift plan is written: the foreman or project manager reviews the variance by cost line
- Monday start-of-shift: the week ahead reflects what Friday's numbers showed
That 48-hour window between Friday totals and Monday kickoff is where a negative-variance week gets a continue signal and a positive-variance week gets a plan adjustment. Without the Friday number, Monday's plan is based on the original estimate, not on last week's actual performance.
On a six-week contract, the first month-end report arrives when roughly 70 percent of the scope is already done. A cost pattern that started in week 2 does not reach the foreman until week 4 or 5. At that point, only 30 percent of the job remains to recover anything.
The person who builds the weekly report does not need to be an accountant. They need the shift tickets, a rate card with loaded labor rates and equipment rates, and a simple spreadsheet. The arithmetic is subtraction and multiplication. What takes time is chasing down missing shift tickets and reconciling mismatched hours between the operator log and the fuel record. Build the habit of catching those discrepancies daily, and the Friday pull takes 30 minutes, not an afternoon.
Reading the variance and acting on it
A positive cost variance means you have spent more than the work done justifies. Two consecutive weeks of positive variance is a trend. Three consecutive weeks is a project that will finish over budget at the current run rate unless something changes.
The useful question is not "how much are we over?" but "which cost line is driving it?" Break the variance down by category:
- Labor cost per unit of production - dollars per ton or per meter
- Equipment cost per unit of production - by machine class
- Fuel per productive hour - by unit number
If labor cost per ton is above estimate but equipment cost is on plan, the crew is not hitting the production rate in the estimate. If equipment cost per ton is above estimate, the machines are cycling slower than planned or carrying higher operating costs than anticipated. Each diagnosis leads to a different corrective action: the crew diagnosis points to cycle time and shift structure; the equipment diagnosis points to maintenance, payload, or haul conditions.
The job cost and margin calculator on this site calculates the weekly variance and projects the final cost at the current run rate directly from your weekly totals. Enter the budget, actual cost, and percent complete, and it returns both numbers without building a spreadsheet from scratch.
A negative variance is not automatically good news. If you are underspending but falling behind schedule, the client will request acceleration. Overtime and additional plant cost money, and a project that looked favorable in week 3 can finish over budget at week 8 if the schedule push drives unplanned costs through the back half of the job.
Where the formula stops working
The cost variance formula applies to fixed-price contracts with a defined scope. Three conditions break it or make the result misleading.
Time-and-materials work: there is no fixed budget, so there is no earned value to calculate against. The equivalent signal on T&M work is cost per unit of production: dollars per ton, dollars per meter drilled, dollars per productive machine-hour. Track that figure weekly against your target rate, and you get the same early warning.
Scope changes mid-contract: if the client issues a variation that changes the total scope, the original budget is no longer the correct denominator. Add approved variations to the budget and restate percent complete before running the formula. A variance calculated against a stale budget tells you how you are performing against a target that no longer exists.
Large front-loaded costs: mobilization fees, camp construction, or major equipment purchases paid in the opening weeks will produce a large positive variance even if production is exactly on plan. Separate those fixed setup costs from the variable production costs and apply the formula only to the variable component until setup costs are fully recovered. A combined variance number during mob is noise that can mask a real production problem underneath it.
Outside those three situations, the formula holds across surface and underground contracting work where the scope is measurable in physical units and the price is fixed.
Run your own numbers
Rather than work it by hand every time, the job cost and margin calculator does this arithmetic and shows its working. The rest of the set is on the mining calculators page.
Common questions
How do you measure percent complete without a formal survey?
Use production units from your daily reports: tons hauled, meters drilled, or cubic meters excavated divided by the total contracted quantity. If the scope is measured in labor-hours, use hours billed to date divided by estimated total hours. The key is using a physical measure, not cost, or the formula becomes circular and hides real overruns.
What does a positive cost variance mean on a mining contract?
A positive variance means actual costs exceed the earned value of work completed to date. It is not a verdict on the final outcome, but it is a flag that something in the inputs is above estimate. Check which cost line is driving it: labor cost per ton, equipment cost per unit, or fuel per productive hour.
Can the cost variance formula work on a time-and-materials contract?
Not directly. The formula requires a fixed budget to calculate earned value against. On time-and-materials work, track cost per unit of production instead: dollars per ton, dollars per meter drilled. That gives you the same weekly early-warning signal without needing a fixed contract price.
Getting this off paper
Most contractors already know these numbers. The cost is in re-keying them into a report, then a timesheet, then an invoice. If that is where your week goes, book a 20-minute call and we will look at your actual paperwork.
