Track direct labor
Count the labor time spent on the job and use a consistent internal labor cost. Employee wages are only one part of labor cost; payroll burden may also matter.
Track materials and subcontractors
Record materials actually used, delivery charges, rentals and subcontractor invoices. Keep allowances separate from final actual costs when reviewing profitability.
Account for overhead
Insurance, vehicles, software, office costs and other operating expenses need to be recovered across the work the business sells. Choose a consistent way to account for overhead in pricing.
Compare estimate to actual
After completion, compare expected labor and material costs with actual results. That feedback improves future estimates far more than guessing from memory.