Engineering Change Cutover Cost Calculator: Immediate vs Run-Out
Every engineering change ends with the same question: do we cut in now and deal with the old stock, or phase in at depletion? This calculator prices both choices and shows the usage rate where the answer flips.
Your numbers
Stock in stores, WIP and open purchase orders that carry the old revision.
The remainder is scrapped or returned.
Scrap value or supplier credit as a share of unit cost.
Cost saving, quality gain or compliance exposure removed by the change, per week.
Your results
Safety, regulatory and customer-mandated changes should not be delayed for cost reasons. Use this only for changes where the timing is a commercial choice.
Immediate vs run-out cost as usage rate changes
Sweeps Weekly usage of the part from 50 to 1000, holding your other inputs fixed.
Stock by revision from your ERP
Optional: we can build a read-only view of stock, WIP and open POs by revision for change decisions.
Optional. The tool and every export work without this. No spam.
How to use it
Enter all inventory that carries the old revision, including open purchase orders and WIP, then split it into reworkable and non-reworkable. Enter the weekly benefit that the change delivers: cost reduction, scrap avoided or warranty exposure removed. The tool prices an immediate cutover (scrap net of salvage plus rework) against the cumulative benefit you give up while consuming old stock.
The formulas
Immediate cost is scrapped units times unit cost times one minus salvage share, plus reworked units times rework cost. Run-out cost is weeks to deplete (stock divided by weekly usage) times the benefit lost per week. The break-even delay is immediate cost divided by weekly benefit. If depletion takes longer than the break-even, cut over now.
Worked example
With 4,200 units at $18.50, 40 percent reworkable at $4.20 and 10 percent salvage, immediate cost is about $47,300. At 250 units a week the stock lasts 16.8 weeks, and with $900 a week of lost benefit the run-out costs about $15,100, so running out is cheaper. At 1,000 units a week the picture changes the other way.
ERP notes and mistakes
In most ERPs the effectivity date or lot/serial cut-in controls the switch, so a run-out needs a clear effectivity rule rather than manual vigilance. A common mistake is ignoring open purchase orders from the supplier, which keep delivering the old revision after you thought you had cut over.
Frequently Asked Questions
When is immediate cutover the right answer?
When the change is safety, regulatory or customer mandated, when old and new revisions cannot coexist, or when the weekly benefit is large compared with the cost of scrapping and reworking old stock.
How do I value the benefit of the change?
Use a measurable weekly figure: material saving per unit times usage, scrap or rework avoided, or warranty cost removed. If the benefit is a risk reduction, use expected loss per week as a conservative estimate.
Should supplier stock be included?
Yes. Include supplier-held stock you have committed to buy and open purchase orders. Cancellation charges or credits can be handled by lowering the salvage percentage or adding them to the rework cost.
Does this include the engineering cost of the change?
No. Engineering effort is the same under both options, so it does not change the comparison. Use the design change cost escalation calculator to estimate the effort side separately.
If you want effectivity, open purchase orders and stock by revision pulled automatically from your ERP for this decision, Netray can help build that read-only view.
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