A lot of contractors find out whether a job made money the same way: after it's over, by comparing what came in to what went out. By then, there's nothing left to do about it. Job costing during the project — tracking budget against actual spend category by category, while the job is still running — is what turns that after-the-fact number into something you can actually act on.
Track by category, not just the whole job
"This job is $2,000 over" doesn't tell you what to do next. "Materials is $800 over because of a lumber price jump, labor is on budget" tells you exactly where to look and whether it's fixable on this job or just a number to remember for the next bid.
Budget vs. actual, updated as it happens
The budget per category comes from your original estimate. The actual comes from real invoices and time as they come in — not estimated, not batched up at the end. The gap between them, updated weekly rather than discovered at closeout, is what gives you a chance to adjust while the job is still in progress.
Remaining budget matters more than total variance
A category running over is a problem. Knowing how much of the overall contract budget is left, after accounting for every category's actual spend so far, is what tells you whether the job as a whole is still healthy — a small overrun in one category is very different news if the job has a big contingency cushion left versus none at all.
Use the template instead of building this from scratch
The Job Cost Tracker Template already has this structure — budget, actual, and variance per category, rolling up into total variance, remaining budget, and variance percentage, all calculating automatically as you update actual costs. Open it in FLYNT Sheets after you win a bid priced with the Construction Estimate Template, and use the same categories in both so the numbers actually line up.