Profit per Machine Hour: A Better Way to Compare Jobs That Fight for Press Time

When a press, cutter or finishing line is full, the best job is usually the one producing the most contribution per constrained machine hour. Revenue per job can reward large but slow orders. Margin percentage can reward attractive-looking jobs that occupy the machine all afternoon. Neither measures what scarce press time earns.

The useful calculation is simple: subtract job-variable costs from revenue, then divide the resulting contribution by all hours the job occupies the constrained machine. Use it only when that work center is genuinely constrained and there is other profitable work waiting for the released time.

Define the unit before calling it profit

Contribution is sales revenue minus costs that change because you accept and produce the job. The SBA uses contribution margin in break-even analysis because contribution first covers fixed costs and then supports profit. The SBA’s break-even guidance provides the underlying distinction.

For job ranking, calculate:

Job contribution = job revenue − job-variable costs

Contribution per constrained machine hour = job contribution ÷ constrained machine hours

This is not the same as operating profit. Operating profit remains after contribution covers fixed operating costs. It is also not cash flow: a job can contribute economically while creating an awkward cash squeeze if materials must be paid for long before the customer pays.

Gross margin is not a reliable substitute either. Gross margin depends on which production costs the shop includes in cost of goods sold, while contribution focuses on costs that change with the decision. If the underlying job records are questionable, fix the inputs with a basic print-shop job-costing process before trusting the ranking.

Count the costs that change with the job

Variable costs commonly include job materials, outsourced operations, packaging, transaction fees, commissions and incremental labor when that labor cost actually changes because of the order. Scrap and expected remake costs also belong when they are attributable to the job.

Rent, existing equipment depreciation, insurance and already-committed salaries may remain payable whether the shop accepts one additional job or not. Those costs still matter to the business, but subtracting the same allocated overhead from every short-run decision can hide which order makes the best use of scarce capacity. Financial and tax accounting may assign direct and indirect manufacturing costs to inventory; that treatment does not determine which costs are avoidable for a specific scheduling decision.

Labor deserves separate attention. A machine can be the bottleneck while hand finishing quietly consumes the contribution afterward. Compare the result with profit per labor hour when people and equipment are both tight.

Count every minute that occupies the constraint

Use one machine-time convention across every job. A practical definition is:

Constrained machine time = setup and make-ready + production run + job-attributable cleanup + expected remake or rework time

NIST defines setup as the time required to prepare a machine or work center for production, and its changeover guidance treats the interval between the last good piece of one run and the first good piece of the next as capacity-relevant. NIST’s manufacturing-time guidance also distinguishes machine operations from transport, delay and inspection.

That distinction prevents an easy spreadsheet mistake: customer lead time is not automatically machine occupancy. Two days waiting in a queue should not become 48 machine hours. Conversely, a 45-minute make-ready does count even though it produces nothing sellable. The press is still occupied; it is merely practicing expensive patience.

A high-margin slow job versus a faster job

Consider two illustrative jobs competing for the same constrained press. These figures are examples, not measured shop results.

Measure	Job A: premium short run	Job B: standard repeat
Revenue	$1,800	$1,600
Variable costs	$600	$800
Contribution	$1,200	$800
Contribution margin	66.7%	50.0%
Constraint time	6.0 hours	2.5 hours
Contribution per constraint hour	$200	$320

Job A wins on revenue, total contribution and contribution-margin percentage. Job B wins on the scarce resource: it produces $320 per press hour instead of $200. If demand is waiting and the press is the bottleneck, Job B creates $120 more contribution for each constrained hour used.

This does not mean Job A is bad. It means Job A should not displace Job B at its current price and production time. The shop could raise Job A’s price, reduce its setup, group it with similar work, schedule it during slack capacity or outsource it. The correct response is often to repair the economics rather than declare the product morally defective.

Stress-test the time assumption

Machine time is often less certain than the material bill. For Job B, the crossover point is easy to calculate:

Maximum hours before Job B falls below Job A = $800 contribution ÷ $200 per hour = 4 hours

Job B remains the better use of the press while its total expected occupancy stays below four hours. If difficult setup, frequent stoppages or expected reprints push it above four hours, Job A takes the lead.

This is why quoted run speed alone is a poor ranking input. Review actual setup, run, cleanup and remake time by product family. Use an expected value for rework rather than pretending it never happens or charging every clean job for one historical catastrophe.

The common trap: ranking work that is not constrained

The Theory of Constraints treats the bottleneck as the resource limiting total system output. The Lean Enterprise Institute’s overview of constraint management also emphasizes that constraints can move. A press-hour ranking is useful only when press hours are scarce and alternative demand can use the released capacity.

If the press sits idle every Wednesday, rejecting a positive-contribution Wednesday job because its hourly rate is unimpressive may leave the shop with less contribution, not more. During slack periods, the relevant question becomes whether the order produces enough incremental contribution without blocking better work or creating downstream problems.

The bottleneck may also be prepress approval, cutting, weeding, packing or skilled operator time. Measure the resource that actually limits output instead of permanently crowning the most expensive machine.

Turn the calculation into a monthly decision rule

Add four fields to each completed job record: contribution dollars, setup time, run time and other job-attributable constraint time. Then review the results monthly by machine, product family and customer.

Identify the work center that actually constrained output during the month.
Calculate contribution consistently from revenue and job-variable costs.
Divide contribution by total occupied constraint hours.
Compare estimated hours with actual hours and correct recurring quoting errors.
Reprice, combine, reschedule or consider outsourcing work that repeatedly falls below the required rate.

A practical target rate can be estimated as:

Required contribution per constraint hour = (monthly fixed costs to recover + target operating profit) ÷ practical monthly constraint hours

For example, if a shop needs $24,000 of monthly contribution to cover fixed costs, wants another $8,000 of operating profit and has 100 practical bottleneck hours, its target is $320 per constrained hour. That is a planning threshold, not a promise: expected sales volume, downtime and work performed away from the bottleneck can all change the required figure.

Use the scarce hour to make the decision

When capacity is tight, rank competing jobs by contribution per constrained hour. Accept or prioritize work above the shop’s required rate, then investigate anything below it: price, setup, batch size, scrap, rework, scheduling and outsourcing are the levers.

When capacity is slack, do not use a constraint metric to manufacture scarcity. A positive-contribution job may still be worth running if it does not displace better work.

The final rule is blunt but useful: when machine time is genuinely scarce, choose the job that earns the most contribution from that scarce hour—not the job with the largest invoice or the prettiest margin percentage.