Gross margin

Revenue minus the direct cost of delivering it, as a percentage of revenue. The number that says whether the work you sold was worth doing.

Gross margin takes each sale and subtracts what it directly cost to deliver: product cost, treatment consumables, the ingredients in the dish. What remains has to cover everything else (rent, marketing, admin) before anything is profit.

Its weekly value is as an early-warning system: revenue can grow while margin slides (supplier creep, discounting, a drifting product mix), which is running faster downhill and is invisible on a revenue-only dashboard. Margin by PRODUCT or SERVICE is where the real decisions live; most businesses discover they have heroes and quiet money-losers on the same menu.

Gross margin sits on the short list in the KPIs guide and drives the arithmetic in the break-even calculator.