Job costing is adding up everything one job cost you, then setting that number against what you charged. That’s it. One job, start to finish, on its own, not the month and not the average across every job you ran. Where people trip is confusing it with bookkeeping, or with pricing. Bookkeeping tells you how the whole business did. Pricing is the guess you make before you ever swing a hammer. Job costing is the receipt that comes after, and it’s the only one of the three that tells you whether a specific job was worth doing.
The definition, and what it isn't
Strip away the accounting words and it’s simple. You take what the customer paid. You subtract what that job actually ate: the hours, the parts, the gas, the little stuff nobody bothers to write down. What’s left is what the job made you. A whole-business profit number can’t tell you that. It blends your winners and your losers into one average, and the average hides the exact thing you need to see, which jobs pull their weight and which ones quietly cost you money just to show up.
The four things that count as cost
Most shops nail the price and blow the cost, because they only count half of what a job eats. Four buckets, and the last two are where the money hides.
Every hour anyone put in, at what that person actually costs you. Not their take-home. The loaded number, with payroll taxes and whatever you carry on top.
Parts, fittings, the box of screws, the dump fee. What you paid at the counter, not what you marked it up to.
The permit, the rental, the sub you brought in, the fuel out and back. Anything that job made you spend that you wouldn't have spent sitting at home.
This job's slice of the rent, the insurance, the truck payment, the phone, the software. Everybody skips it, and it's why a job that looks like a winner often isn't.
Track the first two, miss the last two, and your numbers will look great right up until the bank balance calls you a liar.
One job, run end to end
Here’s the whole thing on a real job. You’re a plumber. Water heater swap, quoted and billed at $2,400.
You and a helper are on it six hours. Loaded, you cost yourself $65 an hour and the helper runs $38. Six hours each: that’s $390 and $228, so $618 in labor. The heater and the fittings came to $900 at the supply house. You pulled a $75 permit and burned about $25 in fuel round trip, so call the direct costs $100. Add the hard numbers, $618 plus $900 plus $100, and you’re sitting at $1,618. Looks like $782 left over. Nice day.
Now the part that gets skipped. Your overhead runs whether you work or not, the rent, the insurance, the truck, the phone, all of it, and spread across the jobs you actually run it lands somewhere near $300 a day. This one took most of a day, so it carries maybe $240 of that load. Knock that off the $782 and you’re at $542. That’s what the water heater really made you. Still a good day, don’t get me wrong. But it’s $542, not $782, and that gap is the number nobody quoted and everybody lives on.
“$782 looked like the profit. $542 was the profit. The $240 you can't see is the part that pays your rent.
The habit is the hard part, not the math
You can read the definition in ten seconds. Doing it on every job is where it falls apart. Run that same receipt job after job for a quarter, though, and the pattern walks right up to you. The water heaters pay. The drain calls, once you count the drive time and the one that came back as a callback, barely clear. You stop guessing which work to chase, because now you actually know which jobs make money.
Where ToolbagCRM fits
The reason shops don’t job-cost isn’t the math. It’s that the pieces live in five places: the hours buried in a text thread, the materials on a receipt in the truck, the invoice in one app, the permit in a drawer somewhere. By the time you’d chase it all down, the next job has started and you’ve given up. Keeping the hours, the materials, the invoice, and the photos on one job record is what makes it happen at all. In ToolbagCRM each job carries its own labor, parts, and billing together, so the receipt adds itself up instead of waiting on you to rebuild it from memory a month later. You can get started free with no card, and Founders is free the first month, then a flat base rate with unlimited users. See plan terms, plug-in slots, and payment fees.