The break-even point is the moment cumulative contribution margin equals the period's fixed costs. Before it, every order is working to cover the base; after it, contribution is profit. In a store it is best read as a day of the month rather than a revenue figure.
Reading it as a date rather than a number is what makes it useful: 'we broke even on the seventh' is a sentence anyone in the business can act on, and how the date moves month over month is a better health signal than most ratios.
It moves when either side moves, so an added subscription or a new hire pushes the date out even if nothing about sales changed. An ecommerce break-even calculator works the date out from your own fixed costs and contribution margin. The monthly break-even worksheet does the same in a spreadsheet.
The margin to feed it is CM3 per order, the one after advertising. Using gross margin makes break-even look days earlier than it is, because it quietly assumes the parcels shipped themselves and the ads were free.
