Job costing without a finance degree
Most shops know how much revenue a job made. The good ones know what it actually cost.
Track labor hours on the job, every job
Even a clipboard. Without job-level labor hours, every other number is a guess. Software helps, paper works.
Tag every material purchase to a job
Photo of the receipt, tagged with the job number. End of week, total per job. That's a 90% accurate cost picture for almost no effort.
Review the worst job every month
Sort jobs by margin, lowest first. Talk about the bottom one in the next leadership meeting. Patterns surface fast.
Take your version of this question further
This is one operator-tested angle on the question. Your shop, your size, your trade, and your team change the answer. Ask your specific version inside Ask a Shop Owner to get a response grounded in how owners like you actually handled it.