Job costing for contractors is the only way to know whether you're actually making money. Most contractors don't go broke from a lack of work. They go broke from a lack of cost tracking on the work they have. A full schedule masks the fact that half your jobs might be breaking even or losing money. If you don't know what a job costs before you invoice it, you're not running a business. You're gambling.

This post is part of our broader look at job costing for contractors. The fixes are plain, but they require you to look at the numbers honestly.

Why do contractors go broke when they're busy?

They go broke because busyness hides bad math, and bad math means you're bidding under your true cost. When you're turning down jobs and working Saturdays, it feels like success. But if your bids are based on gut rather than actual costs, volume just multiplies the loss.

I see it constantly. A contractor prices a kitchen remodel at $40,000. He thinks he cleared $10,000. He spends it on the next truck payment. He never accounted for the two days his lead carpenter spent on callbacks. He forgot the fuel for the dumpster runs. He didn't allocate any of the shop rent or insurance to that specific job. The profit he thought he made was $10,000. The real number was closer to $2,000. It might have been negative.

The trap is thinking that more jobs equals more profit. It only works if every job carries its own weight. One bad bid doesn't hurt once; it hurts every time you replicate it.

What exactly should you include in a job cost?

Everything that would disappear if that specific job didn't exist. That means direct labor, direct materials, subcontractors, permits, and equipment rental tied to the project. It also means a portion of your overhead — vehicle insurance, shop rent, tool depreciation, office phone — applied across your jobs realistically.

What does not belong in the job cost? Your owner's draw, personal vehicle use unrelated to that project, and company-wide marketing spend. Those are business expenses, but they aren't caused by that job. Mixing them in makes you think your crews are less efficient than they are.

The IRS lets you deduct ordinary and necessary business expenses under IRC §162. Job costs that go into your cost of goods sold — direct labor, materials, subcontractor payments — come off your revenue before tax is calculated. Get this number wrong and your Schedule C or Form 1065 overstates profit, which means you overpay tax and overestimate what you can spend.

True job costing tracks each category separately so you can see where the bleed starts. Labor is almost always the biggest piece, and it's the easiest to underestimate.

How do you figure out what an hour of labor really costs?

An hour of labor costs more than the hourly wage. It includes payroll taxes, workers compensation, benefits, and the non-billable hours you still pay for. A carpenter earning $30 per hour on the paycheck actually costs you more. You also pay employer payroll taxes, workers compensation, liability insurance tied to payroll, and any benefits. If you don't add those up and divide by the actual billable hours, you're flying blind.

Start with the annual cost. Take wages plus taxes, comp, and benefits. A typical all-in cost might run $75,000 per year for that carpenter. Then divide by the number of hours that person will actually be on a job site producing billable work. A full-time employee has 2,080 available hours on paper. After vacation, holidays, training, and drive time, the real billable hours might only be 1,700. Divide the annual cost by the real hours. That gives you a loaded cost closer to $44 per hour. Your base wage was $30. The gap is what you missed.

You bid at $36 an hour. Your loaded cost is $44. You lose $8 on every hour. On a 200-hour job, the loss adds up fast. You are out $1,600 before you buy a single 2x4.

How much profit should a job have before overhead?

Gross profit — job revenue minus direct job costs — needs to be high enough that your overhead doesn't wipe it out. Most trade contractors need gross profit in the 35% to 50% range depending on the trade. Lower than that, and your fixed costs eat you alive.

Here's the sequence. Job revenue minus direct costs equals gross profit. Gross profit minus overhead equals net profit. Net profit is what you actually keep. If you skip the first step and just look at the bank balance, you never see which jobs are carrying the company and which are dragging it down.

Markup and margin are not the same thing, and confusing them is how you end up with 20% less money than you expected. Thirty percent markup on cost does not equal thirty percent margin on revenue. It equals roughly twenty-three percent margin. The difference is seven points of profit you never see.

What's the fastest way to start job costing without new software?

You don't need enterprise software. You need discipline. Give every job a name or number. Have every employee clock in and out by job, including drive time. Collect material receipts daily and staple them to a job folder. At the end of the week, add up labor, materials, subs, and fuel for that job. Compare it to your bid.

If you use QuickBooks, turn on class tracking or use projects. If you use paper, use a spreadsheet. The tool doesn't matter as much as the habit. What matters is that you stop saying "we made money on that job" and start saying "that job produced $4,200 in gross profit, which is 38% of revenue."

Cash or accrual, the job costing works the same: match the costs to the job in real time, not when the credit card bill arrives.

What a $15,000 Job Looks Like Two Ways

The table above is illustrative, but the pattern is real. Contractors who don't allocate overhead and loaded labor think they are profitable until the year-end profit and loss shows otherwise. By then, the money is spent.

How do you stop losing money on the next job?

Review every completed job within a week of closing it out. Not at tax time. Not when the check clears. Within a week. Compare actual hours to estimated hours. Compare actual material pulls to the original takeoff. Note every variance.

If a job went over, figure out why. Was the estimate wrong? Did the client add scope without a change order? Did your crew lose time to a supply run that should have been delivered? Write it down. That document is now your bidding bible for the next similar job.

Bidding accurately starts with knowing what the last one cost. If you don't have that data, you're just repeating the same mistake with more volume.

Change orders are another leak. Every deviation from the original scope needs a signed price before the work happens, not after. Clients who know you won't charge for small extras will ask for them indefinitely. Those extras have labor and material costs. If you eat them, you are paying to work.

How does job costing tie into your taxes and your pay?

Job costing determines your true cost of goods sold, which drives the profit number you report on Schedule C or Form 1065 and the tax you actually owe. When you know your true gross profit per job, your books reconcile cleanly. Your tax set-aside becomes a simple percentage of actual net profit instead of a guess based on bank balance.

Equipment bought for a specific job may qualify for §179 expensing or bonus depreciation, but only if you can show it was placed in service for that project. Job costing records are the proof the IRS expects if you claim a write-off tied to that work.

It also protects your own paycheck. Paying yourself from a net profit you can actually see is sustainable. Paying yourself from gross revenue while ignoring job costs is how you end up unable to make payroll in February.

What are the most common job costing questions?

For more on protecting your profit, see our main guide to job costing for contractors.

Running a full schedule but can't tell which jobs actually pay you? We help contractors build job costing systems that show true profit per project, clean up the books, and keep more of what's yours. Book a meeting with our team here.