Calculating Factory Cost Per Minute SOP

Cost Per Minute, universally shortened to CPM in garment costing, is the price of one minute of factory time. It answers a single question: when the whole factory runs for one minute, how much does that minute cost? Every salary, every unit of electricity, every taka of rent and depreciation is squeezed into that one number, and that number then prices every garment the factory makes.

The reason CPM matters so much is that garment pricing is really time pricing. A buyer does not pay for cloth and thread alone; the buyer pays for the minutes a factory spends cutting, sewing, finishing, and packing. The SMV of a garment counts those minutes. CPM prices them. Multiply the two and you get the labour cost of making the garment, which merchandisers call CM, the Cost of Making. Get CPM wrong and every quotation in the factory is wrong in the same direction, month after month.

A useful mental model is to think of the factory as selling minutes. Each month it buys a fixed stock of minutes from its workforce and its building, and it sells those minutes back to buyers inside garments. CPM is the break-even price of a minute. Anything charged above CPM on a garment contributes to profit; anything charged below it consumes the factory's own money.

Step one is collecting the expense total. Open the finance ledger for the previous month and add up every factory operating expense: direct wages for operators and helpers, indirect wages for supervisors, quality checkers, and maintenance staff, factory rent, electricity and utilities, management salaries, depreciation on machines and building, maintenance and spare parts, and administration. Use actual figures, not budgeted ones, because a quotation built on a budget inherits every budgeting error.

Step two is counting working days and shift minutes. A standard month in a Bangladesh garment factory has 26 working days, and a standard shift is 8 hours, which is 480 minutes. If the factory runs overtime regularly, record overtime minutes separately rather than folding them into the base shift, because overtime minutes carry a different wage rate and mixing them distorts the base CPM.

Step three is computing total available minutes. Multiply the number of operators on the payroll by working days by shift minutes. With 500 operators, 26 days, and 480 minutes, the result is 6,240,000 available minutes. This figure assumes every operator attends every shift, which is why it is only a starting point.

Step four is dividing expense by available minutes. This gives CPM at 100 percent attendance. It is a useful diagnostic number because it shows the cheapest a minute could ever be in this factory, but it must never be used for quotation, since no factory achieves 100 percent attendance across a whole month.

Step five is adjusting for target efficiency. Multiply available minutes by the planned line efficiency to get produced minutes, then divide the same expense by produced minutes. This is the quotation CPM. It is higher than the 100 percent figure by exactly the efficiency gap, and that gap is real money: salaries are paid for attended minutes, but output is earned only from produced minutes.

All figures in this example are illustrative, chosen to make the arithmetic transparent. Shams Apparels closed the previous month with a total factory operating expense of BDT 12,480,000. The expense table in this lesson shows the build-up: direct wages BDT 5,400,000, indirect wages BDT 1,800,000, rent BDT 1,200,000, electricity BDT 900,000, management salaries BDT 1,500,000, depreciation BDT 600,000, maintenance BDT 300,000, and administration BDT 780,000. Added together they equal BDT 12,480,000.

The factory runs 500 sewing operators on a 26-day month with an 8-hour shift. Daily minutes per operator are 8 times 60, which is 480 minutes. Monthly available minutes are 500 times 26 times 480, which is 6,240,000 minutes. CPM at 100 percent attendance is BDT 12,480,000 divided by 6,240,000, which is BDT 2.00 per minute.

Management plans at 80 percent line efficiency, based on the previous quarter's actual performance. Produced minutes are therefore 6,240,000 times 0.80, which is 4,992,000 minutes. Quotation CPM is BDT 12,480,000 divided by 4,992,000, which is BDT 2.50 per minute. The difference between the two figures is BDT 0.50 per minute, and that difference is the cost of the 20 percent of minutes that are paid for but produce nothing.

Now apply the quotation CPM. A T-shirt with an SMV of 4.50 minutes costs 4.50 times 2.50, which is BDT 11.25 in labour cost. Quoted at the 100 percent CPM instead, the same shirt would be priced at 4.50 times 2.00, which is BDT 9.00, understating labour cost by BDT 2.25 per piece. On a 100,000-piece order that is BDT 225,000 of cost the factory absorbs without ever seeing it on a quotation sheet.

CPM is not a constant of the factory; it is a monthly measurement. Four forces move it. Attendance moves it first: a month with heavy absenteeism, festival leave, or illness spreads the same salary bill over fewer minutes and pushes CPM up. Headcount moves it second: hiring 50 operators without a matching rise in orders spreads fixed costs thinner and pushes CPM down, but only if those operators actually produce. Expense moves it third: a wage revision, a rent increase, or a power tariff hike raises the numerator overnight. Efficiency moves it fourth: a difficult style mix or a new-buyer learning curve lowers produced minutes and pushes CPM up even when nothing else changes.

The sensitivity table in this lesson makes the point numerically. Holding the expense at BDT 12,480,000, CPM is BDT 2.86 per minute at 70 percent efficiency, BDT 2.67 at 75 percent, BDT 2.50 at 80 percent, and BDT 2.35 at 85 percent. A five-point efficiency swing moves CPM by roughly BDT 0.17 to BDT 0.19 per minute, which on a shirt with an 18-minute SMV is more than BDT 3.00 per piece. Factories that quote on a stale CPM are therefore repricing their whole order book every time efficiency drifts.

The discipline that prevents this is a monthly CPM routine. On the first working day of each month, the IE manager and the accounts manager sit with two documents: the previous month's expense ledger and the attendance register. They recompute CPM, compare it with the previous month, and write one line explaining any movement larger than the normal range. That one line is often the earliest warning of a real problem: a creeping power bill, a supervisor vacancy filled with overtime, or an attendance slide nobody noticed.

The most expensive error is quoting from the 100 percent figure. It feels conservative to use the lower number, but it is the opposite: it guarantees that every order loses the efficiency gap. The second error is using payroll headcount instead of attended minutes. Headcount flatters the denominator in every month with absenteeism, which is every month. The third error is an inconsistent cost base: including helper wages in the numerator while excluding helper minutes from the denominator, or the reverse. Either inconsistency makes CPM drift for reasons that have nothing to do with factory performance.

A fourth error is treating depreciation as if it were not a cost because it is not a cash outflow. Depreciation is the monthly price of the machines and building, and a factory that ignores it will happily quote prices that never repay its capital. A fifth error is adding profit twice: building a margin into the CPM and then adding a margin percentage on top of CM. One margin, stated once, is the honest approach, and it keeps the quotation sheet readable for the buyer.

Before any CPM figure leaves the factory, check five things. First, the expense total ties to the finance ledger for the same month. Second, the minute base uses attended minutes, not headcount. Third, the efficiency figure comes from recent actual performance, not from the target the factory wishes it could hit. Fourth, the sheet shows both the 100 percent figure and the target-efficiency figure, clearly labelled, so nobody mistakes one for the other. Fifth, the previous month's CPM is shown beside the new one with the movement explained in one line. A CPM sheet that passes these five checks is a safe basis for every quotation that follows.