What is post-calculation?

An installation firm quotes for a job, expecting a certain number of hours and a certain amount of material. When the job is done you want to know whether that was right. Checking afterwards is post-calculation.

It starts with the quotation, which holds what you estimated up front. During the project you record the hours, materials and costs that really belong to it. At the end you set the two side by side and see, per project, whether you made a profit or a loss and where the difference sits.

Without it you do not know. Every project looks fine because an invoice goes out, while a part of your work is consistently priced too low. You only notice in the annual accounts, and by then it is hard to trace which kind of work lost money.

Watch three things. Hours must be booked on time and to the right project, or the result is wrong. Costs you do not tie to a project, such as purchases or subcontracting, disappear into general overheads. And a good comparison uses the same breakdown as the original estimate, for instance the same cost price and cost object structure, otherwise you compare unlike things.

The value lies in what you do with it. Use the outcome to estimate your next quotation better, to see which customers or kinds of work earn the most, and to adjust while a project is still running.

Keep it simple at first. Pick one kind of project you do often, record hours and costs for it consistently, and compare with the quotation after each project. After a few projects the patterns show themselves.