Job Costing for Contractors: How to Track Costs and Protect Your Profits

You finished a job. The client paid. But did you actually make money? Too many contractors can't answer that question confidently.

What is Job Costing?

Job costing means tracking every expense tied to a specific project. At the end, you know exactly how much you spent on materials, labor, subcontractors — and your actual profit margin.

Why It Matters

• Know your real margins — That $45K kitchen remodel: 20% margin or 5%?
• Bid more accurately — Past data = confident future quotes
• Spot problems early — Catch overruns before the invoice
• Find your best work — Which job types are actually profitable?

How to Implement

1. Set up job numbers — Every project gets a unique ID
2. Track all costs by job — Materials, labor, subs, equipment
3. Compare to estimates — Where were you off? Why?
4. Review and adjust — Improve future estimates

Common Mistakes

• Forgetting small purchases (those $50 Home Depot trips add up)
• Not including labor burden (taxes, insurance, benefits)
• Ignoring overhead allocation
• Waiting too long to enter data

Example

Without job costing, you'd just see $45K revenue and feel good. With it, you see what really happened.

Getting Started

You don't need complex software. Start simple — even a spreadsheet beats guessing. Then upgrade to dedicated tools as you grow.