A harder question than it looks
"Did that job make money" sounds like it should be a one-line sum (what you charged minus what you bought for materials), but that's a much thinner version of the question than the one that actually matters. Two costs routinely go missing from that back-of-envelope figure. The first is rework and callback time: if you had to go back and fix something, or a customer called you out again for a problem with the original job, those hours are a real cost of that job, but they usually get absorbed into "just part of doing business" rather than tracked against the specific job that caused them. A job that looked profitable on the day can turn into a loss once the callback is counted properly, and if nobody ever adds that hour back in, the job keeps looking profitable on paper forever. The second is travel and vehicle cost: getting to a job, loading and unloading, running the ute. That time and expense is genuine cost to the business, and a lot of pricing simply ignores it, treating the job as though it started the moment tools came out rather than the moment you left the last one. Add both back in and a job that looked comfortably profitable at a glance can turn out to have barely broken even, or worse.
Costing a job properly means working from price charged down to an actual profit figure: subtract materials, subtract all the labour that job consumed including rework, subtract travel, and see what's left as a percentage of what you charged. That figure (the margin, not the raw dollar profit) is what lets you compare one job against another regardless of size, and it's the number that tells you honestly whether a type of job, or a particular customer, is worth taking on again at the price you quoted.
The costs that quietly don't get counted
Rework and travel are the two biggest gaps, but they're not the only ones. A few more that routinely slip through the cracks on a back-of-envelope job cost.
Loading and unloading time, at the yard, the supplier, and the job itself, is real labour that a job consumes before any tool comes out. An apprentice or offsider standing around waiting for materials, waiting for you to finish a quote on the last job, waiting because the previous job ran long, is being paid for that time whether or not it shows up against a specific job. Tip fees for anything you cart away are a real cost per load, not an occasional annoyance. Machinery hire, whether it's a mini excavator for an afternoon or a generator for a weekend job, gets forgotten more often than materials do, probably because it doesn't sit on a supplier invoice the way materials do. And the ute itself, fuel, servicing, tyres, registration, insurance, is a genuine cost of running the business that a lot of pricing quietly assumes is free because nobody wrote a cheque for it on the day.
Warranty callbacks deserve their own mention, separate from rework on the original job. A customer ringing eight months later because something you fitted has failed is a cost against the original job, even though the invoice for that job was paid and closed out long ago. Most trades absorb this as a cost of doing business, which is fair enough, but it's worth at least knowing roughly how often it happens and against which type of job, because a job type with a high callback rate is quietly less profitable than its invoices suggest.
Overhead: why a profitable job can still not cover the business
Here's the part that catches a lot of tradies out. A job can clear a healthy margin, materials, labour, travel and rework all subtracted, and the business as a whole can still be losing money. That's not a contradiction. It's overhead.
Rent on a shed, insurance, accounting fees, software subscriptions, the phone bill, a bookkeeper's time, none of that attaches to any single job, but all of it has to be paid out of the combined margin every job earns. If your jobs average a 25% margin and your fixed overhead eats 20% of revenue just to keep the lights on, you're left with 5% actually landing as profit, and that's before anything goes wrong. A single job that comes in at 25% margin looks fine in isolation. Whether the business as a whole is fine depends on how many jobs like it you run in a month against how much overhead sits above them, a question job costing alone doesn't answer but sets up the numbers to answer. Getting a clear read on overhead, and what it's actually costing against revenue, is exactly the kind of unglamorous bookkeeping our back office support work is built around.
Deciding what counts as a job cost, and sticking to it
There's no single correct rule for exactly where a job's costs start and stop. Does travel time get counted from the moment you leave home, or only between jobs? Does the ute get charged against a job by the kilometre, or as a flat daily rate regardless of distance? Reasonable businesses answer these differently, and that's fine.
What actually matters is picking an answer and using the same one every time. A job costed one way in January and a different way in June can't honestly be compared, and the whole point of costing jobs is being able to compare them, one job type against another, one customer against another, this quarter against last quarter. Write your rule down somewhere you'll actually look at it again, even if it's just a note in the same place you keep your rates, so the next person costing a job (including future you, six months from now) uses the same yardstick as the last one.
What to do with a job type that keeps losing money
Once you're costing jobs consistently, a pattern usually turns up, and it's not always the job type you'd have guessed. Small emergency callouts, jobs for a particular customer, or work using a particular supplier can all quietly run at a loss while looking busy on the calendar.
When that happens, there are really only three honest options. Reprice it, if the market will bear a higher rate for that type of work. Stop offering it, if it can't be repriced without losing the work entirely and it's not worth keeping as a loss leader. Or work out why, specifically, before doing either, because sometimes the loss traces to one supplier, one recurring problem, or one customer, rather than the job type itself. What doesn't work is noticing the pattern and doing nothing, because a job type that loses money at ten jobs a year loses considerably more at fifty.
The GST point that skews the number
There's one detail in that materials figure that's easy to get wrong and quietly overstates cost every time it happens. If you're GST-registered, the Australian Taxation Office's GST framework means GST-registered businesses can generally claim a credit for the GST paid on business purchases, materials included. That GST isn't a real cost to the job; it's money you get back through your Business Activity Statement, separate from the job itself. So if you enter a materials figure that already includes GST and use it as-is in a cost calculation, you're treating roughly a tenth of that spend as a real cost when it isn't, which overstates your true cost and understates your actual margin on every job you cost that way. The fix is simple once you know to look for it: back the GST out of a GST-inclusive materials figure before it goes into the sum, and use the ex-GST amount as the real cost. This calculator does that conversion for you if you tell it which way the figure you entered was quoted. It is the same "ex GST or inclusive" distinction that trips people up on quotes generally, not just here.
Why this doubles as record keeping
There's a second, less obvious payoff to costing every job properly: it forces the habit of keeping the paperwork a job generates (the quote, the invoice, and materials receipts) together and attached to that job, rather than scattered across a shoebox or a phone camera roll. That habit matters beyond this calculator. The Australian Taxation Office's own record-keeping rules require most business records to be kept for 5 years, and a quote, invoice or receipt tied to a job you costed and later disputed (a customer chasing a refund, a tax review, a warranty claim) is exactly the kind of record those rules are about. A business that costs every job as routine has, almost as a side effect, already built the filing habit the ATO expects; one that only works it out roughly in its head, if at all, usually hasn't. Neither costs much time on any single job, but only one leaves you with an answer, and a paper trail, if the question gets asked years later.
Making this a system, not a spreadsheet
Costing one job by hand, occasionally, tells you something about that job. Costing every job, consistently, tells you something about the business (which types of work are actually worth taking, which customers or jobs quietly eat more rework than others, and whether your pricing has kept pace with what materials and labour cost now, not what they cost when you last set your rates). That only happens if job costing is a system, not a one-off done when something feels off, the kind of ongoing quoting-and-costing habit our business systems work is built around, capturing the numbers as a job happens rather than reconstructing them from memory afterwards. Profitability only means anything against a pricing structure that reflects your real costs in the first place, worth checking against our pricing page, and against the leads a well-built SEO presence brings in, which are worth costing the same as any other job rather than assumed profitable by default.