CM Costing from First Principles
CM, the cost of making, is where garment factories win or lose quotations, and it is routinely computed by copying last season's number and adjusting by feel. The honest calculation has exactly three parts, and each part hides a decision.
The formula
Cost of making per piece equals the garment's SMV, times the cost of one minute of your factory, divided by the efficiency you actually run. Three numbers. All three are commonly wrong.
The SMV. If it was measured by work study, it is a fact with a date. If it was typed from memory or copied from a similar style, it is a guess wearing a fact's clothes, and every error in it passes straight into the price. We wrote about this distinction in measured SMV versus typed SMV; it decides more quotations than the negotiation does.
The minute cost. Take everything the sewing floor costs per month: wages and benefits, supervision, power for the machines, depreciation, the floor's share of rent and overheads. Divide by the minutes the floor actually attends. Factories that only count operator wages understate the minute by a third and then wonder where the margin went. The cost-per-minute calculator walks the parts.
The efficiency. The divisor that turns theoretical minutes into real ones. Quote at 65 percent while running at 52 and every order ships with a hidden discount you never agreed to. The efficiency in the quote should be the measured average of the line family that will sew it, and it should be written on the costing sheet so the assumption is visible.
Run it both ways
The CM-per-piece calculator makes the arithmetic instant, which frees attention for the decisions. Run every serious quote twice: once at the efficiency you hope for and once at the efficiency you last measured. The gap between the two prices is your risk on the order, in currency. If the buyer's target only works at the hopeful number, you are not quoting; you are betting.
What to fix first
The order of leverage is stable across factories. First, know your minute cost properly; it changes rarely and mispricing it poisons everything. Second, move your top styles from typed to measured SMVs. Third, state efficiency explicitly on every costing sheet. A factory that does these three things still negotiates hard, but it negotiates knowing where zero is, and that alone pays for the discipline many times a year.