Purpose
Post-calculation answers two fundamental questions: Was this project profitable? And: Which assumption in the pre-costing estimate was inaccurate? The second question is often the more valuable, as its findings directly inform every future quote, proposal, and client contract.
Database & Required Data
Carrying out an accurate post-calculation requires comprehensive records:
- The actual hours worked per person and activity
- The corresponding internal cost rates and charge-out rates
- Subcontractor and third-party services
- Project-specific direct material and operational expenses
The critical dependency is almost always precise working time tracking. If employees log hours only approximately or retrospectively, post-calculation quickly degrades into guesswork. From a UK compliance perspective, accurate time and payroll records also ensure that working patterns comply with the Working Time Regulations 1998 and verify that actual hours worked maintain statutory remuneration above the National Minimum Wage.
Typical Causes of Variance
| Cause | Distinguishing Feature |
|---|---|
| Scope Creep | Effort increases, but additional deliverables were never formally agreed via a change request |
| Incorrect Resource Allocation | Senior fee-earner hours logged against a role estimated at junior level |
| Rework & Rectification | Disproportionate hours logged during final QA and delivery phases |
| Underestimated Project Administration | High proportion of non-billable coordination, stakeholder management, and internal meetings |
| Inaccurate Overhead Absorption Rate | Systematic variances recurring across multiple projects |
Feedback Loop
A post-calculation that is not fed back into subsequent pre-costing models is wasted effort. Organisations should establish a structured review cycle in which charge-out rates, staffing ratios, and delivery assumptions are systematically audited and adjusted based on the post-calculations of the preceding financial period.
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