Capture the job facts before the calculation
Start with the vehicle or asset, service type, condition, location, requested extras and timing. These details influence the time, products and travel needed, so they should be visible rather than buried in a single total.
Where a condition cannot be confirmed before the job, record that uncertainty. A calculator can compare assumptions; it cannot inspect the asset for you.
Separate direct inputs from general overhead
Direct inputs may include job-specific labour, consumables, travel and subcontractor work. General operating costs should not be quietly treated as zero simply because they are harder to allocate. Use a documented approach that suits your business and seek professional advice on accounting treatment if required.
The purpose is not to produce one universal number. It is to make the price assumptions reviewable before a commitment is made.
Review the margin as an assumption
A contribution-margin view can help show how a proposed price compares with the costs you have entered. It does not calculate tax obligations, replace bookkeeping or confirm that every future job will produce the same result.
After a job, compare the original assumptions with what happened in practice. That feedback loop is more useful than treating the first estimate as permanent truth.
Use an Excel-first workflow carefully
DetailMargin is an Excel workbook with calculators, dashboards, blank/demo workbooks and implementation guidance for mobile detailing job costing, margin tracking and profitability planning.
Microsoft Excel desktop is required for the intended workflow. Google Sheets compatibility is not verified, and the workbook is not accounting or tax software.