Job Costing for General Contractors: What It Is and Why Most Skip It

You finished a job. You got paid. You moved on to the next one. But do you know if that job actually made money?

Not whether the invoice cleared. Whether the job — after labor, subs, materials, equipment, permits, and overhead — produced a profit worth doing it for.

Most general contractors cannot answer that question with a number. They know their bank balance. They know what they billed. But the per-job margin calculation — the one that would tell them which jobs to take more of and which to stop bidding — is missing.

Why QuickBooks does not solve this

QuickBooks is an accounting tool. It is built to track where money went, produce financial statements, and help your accountant at tax time. It does all of that well.

What it does not do well is show you profitability at the job level. To get a per-job P&L out of QuickBooks you need to be disciplined about job costing setup from day one — cost codes, classes, jobs — and most contractors either set it up wrong or do not set it up at all.

The result is a clean set of books and no idea which jobs made money.

What job-level margin actually tells you

When you can see margin per job, a few things become clear immediately:

Which job types are worth taking. If your residential remodels consistently run at eighteen percent margin and your commercial tenant improvements run at nine percent, that is a pricing or bidding problem worth fixing.

Where costs are running over. A job with good revenue but bad margin is usually a labor overrun, a materials overage, or a sub that came in higher than estimated. When you see it at the job level, you can identify the pattern.

How to bid the next job. Historical margin data is the best estimating tool you have. If you know what similar jobs actually cost — not what you estimated, what they actually cost — your next bid will be more accurate.

The overhead allocation problem

One reason per-job margin is hard to calculate is overhead. Your truck, your insurance, your office, your phone — none of that maps cleanly to a specific job. Most contractors either ignore it or use a rough percentage.

The right approach is to allocate overhead as a percentage of revenue across all active jobs. It is not perfect, but it gives you a net margin number that reflects the full cost of running the business, not just the direct job costs.

Getting started

The fastest path to job-level margin visibility is a transaction export from your accounting tool with a job or project column. Every revenue and cost transaction tagged to the job it belongs to.

Upload that to Margn and it breaks down margin by job automatically — revenue, labor, subs, materials, equipment, overhead, net profit. No setup, no formulas, no pivot tables.

Download the general contractor sample file to see the format, or get started free and upload your own data.

Not ready to upload yet? Start with the Service Business Profitability Calculator — a pre-built Excel template that shows your job margin in minutes, no setup required. Or track your monthly cash position with the Small Business Cash Flow Dashboard.