What job costing is
Job costing answers a blunt question: after labour, materials and the other costs that belong to this job, what is left? If you only look at revenue for the month, a busy week can still be a bad week.
The unit is the job. Not the week. Not the crew. The bathroom exhaust and four downlights at 14 Oak Street either made money or they did not.
The three buckets
Keep the buckets boring. Fancy categories are how costs go missing.
- Labour: hours on the job, including travel if you actually charge it that way
- Materials: what you bought or pulled from the van for this scope
- Other: call-out, parking, permits, subcontractors — anything that would not exist without this job
Margin is not markup
Markup is what you add on top of cost to get a price. Margin is what is left after cost as a share of the price. Mixing the two is how a quote looks healthy and the invoice does not.
Run the numbers on paper or in the profit margin calculator before you send the quote. Do not invent an hourly rate you do not use. Use your own.
When costing happens
Before the quote: a planned cost. After the job: actual hours and receipts. The gap between those two is the lesson. If you never record actuals, every future quote is still a guess.
A marked example lives in the how-to-price-a-job guide — same Oak Street bathroom, same documents. Costing is the arithmetic behind those papers.