1. Define what you need to measure
Start with the right unit: a product, order, project or service. Define which costs can be attributed directly and which shared costs need allocating. Cost centres and consistent allocation rules make the model verifiable, rather than simply more detailed.
2. Build a realistic estimate
Estimate the materials, working time, energy and other resources required. Include relevant overheads, with explicit assumptions about volumes and capacity. The model should allow prices and consumption to be updated without hiding the underlying assumptions inside a single average cost.
3. Compare the estimate with execution
Use the consumption and costs actually recorded for the same object of analysis. Separate price, consumption, time and volume variances. Check data quality first: a difference may reflect an operational issue, but it may also result from incomplete records or an unsuitable allocation rule.
4. Connect differences to decisions
Analysis becomes useful when it leads to action: revising a quotation, reviewing consumption, redesigning a workflow or renegotiating terms. Track margin and cash collection separately; a project that is profitable on paper may require cash before its revenue is collected.