Ask a service business owner which jobs made money last month, and most will name their two biggest invoices. Ask them which jobs lost money, and you'll get a shrug. That gap is where margin quietly dies.
The five inputs a job costing system needs
- Labor hours per employee, tied to the specific job
- Fully-loaded labor rate (wage + burden + benefits + non-billable time)
- Materials and parts used, at true landed cost
- Equipment and vehicle allocation (per-hour or per-job)
- Any subcontractor spend tied to the job
Miss any one of these and the number is a guess. Get all five and you have a decision-grade profitability figure per job.
The formula you actually run
Gross margin per job = invoiced amount − (labor cost + material cost + allocated overhead). Divide by invoiced amount for margin percentage. Sort your last 90 days of closed jobs by that percentage.
What the sorted list tells you
The bottom quintile is almost always the same shape: undersized jobs booked at the standard rate, jobs that required a second visit, or work for a customer whose scope creep isn't priced in. The top quintile is usually the opposite: right-sized work, first-time-right, and clean scopes.
Run it weekly, not monthly
Monthly job-cost reviews are hindsight. Weekly reviews are steering. Every Friday, pull the week's closed jobs, flag anything below 20% gross margin, and ask two questions: was this priced wrong, or executed wrong? Different answers lead to different fixes — pricing changes vs. training.
"The week we started flagging sub-20% jobs on Friday, we found a single customer eating a quarter of our labor budget. We re-priced them the following Monday."
Where the software matters
Job costing is only as good as the labor and material data flowing into it. If techs are logging hours from memory at the end of the week, your job costs are fiction. Real-time clock-in on the mobile app, materials scanned or logged at the truck, and a fully-loaded rate maintained centrally — that's the setup that makes weekly reviews possible.
Job costing is not a report. It's a habit. The service businesses that grow past their first plateau are almost always the ones that made this habit weekly, non-negotiable, and boring.