Engineering & PLMFree calculatorPDF, Excel, Word exportDiscrete Manufacturing

Engineering Change Cost Impact Calculator

An engineering change is rarely just the cost of the engineer's time. Stock that becomes obsolete, rework, tooling and requalification often dwarf labor. This calculator adds them up and shows the payback against the savings the change is meant to deliver.

Your numbers

Engineering effort

hours

Design, analysis, testing support and review time.

Loaded engineering rate

$/hour

Documents and records to update

docs

Drawings, BOMs, routings, work instructions, inspection plans.

Time per document

hours

Affected stock and WIP

units

On hand, in process and on open orders that cannot be cancelled.

Unit cost of affected parts

Share to be scrapped

Scrap plus rework share should not exceed 100%.

Share to be reworked

Rework cost per unit

New tooling and fixtures

Requalification and testing

Annual saving per unit produced

$/unit

Material, labor, warranty or scrap savings after the change.

Annual volume

units/year

Your results

Total one-time cost

$32,190

Payback period

16.1 months

Zero means there is no annual benefit to pay back the cost.

Engineering and documentation labor

$7,410

Scrapped stock write-off

$10,200

Cost of stock and WIP that cannot be used after the change.

Rework cost

$2,080

Annual benefit

$24,000

Net benefit after 3 years

$39,810

Planning estimate based on your inputs. It excludes cost of capital, customer re-approval fees, warranty exposure and schedule delay unless you include them in the inputs. Use actual ERP stock and open order quantities where possible.

Save results:

Payback (months) vs annual volume

Sweeps Annual volume from 2000 to 60000, holding your other inputs fixed.

Get real stock exposure for each change

Optional: we can look at how on-hand, WIP and open PO exposure could be calculated automatically per change from your ERP.

Optional. The tool and every export work without this. No spam.

How to use the calculator

Enter the effort to design and document the change, the number of documents to update and the loaded hourly rate. Then enter the stock and work in process affected, its unit cost and how much will be scrapped or reworked. Add tooling, fixtures and requalification or test costs. Finally enter the annual saving per unit and annual volume. The calculator shows total one-time cost, annual benefit, payback in months and net benefit over three years. The chart sweeps volume so you can see how sensitive the decision is to forecast. Take affected stock from your ERP rather than guessing.

Include open purchase orders you cannot cancel in affected stock
Use fully loaded rates, not base salary
Keep scrap plus rework percentages at or below 100
Test the result at low, base and high volume

The formulas

Labor is (engineering hours + documents times hours per document) times the rate. Write-off is affected units times the scrap share times unit cost. Rework is affected units times the rework share times rework cost per unit. One-time cost is the sum of labor, write-off, rework, tooling and requalification. Annual benefit is saving per unit times annual volume, and payback in months is one-time cost divided by annual benefit times twelve. Net benefit after three years is three years of benefit minus one-time cost. There is no discounting, which is acceptable for short paybacks but understates cost for long ones.

Worked example

With the default inputs, labor is (60 + 12 x 1.5) x 95 = 7,410. Scrapped stock is 800 x 30% x 42.50 = 10,200, and rework is 800 x 40% x 6.50 = 2,080. Adding 8,500 tooling and 4,000 requalification gives a one-time cost of 32,190. Annual benefit is 1.20 x 20,000 = 24,000, so payback is about 16 months and the three-year net benefit is about 39,800. If volume halves, payback roughly doubles, which is exactly what the chart shows. This helps a change board see whether the saving case is robust.

Common mistakes

The most common mistake is counting only engineering hours and ignoring the write-off of stock that cannot be used. The second is optimistic savings that ignore the fact that the saving might be partly offset by higher purchase price or cycle time. The third is forgetting that timing matters: a use-up effectivity can reduce write-off to almost zero, which is why the effectivity choice on the ECO is a financial decision. Finally, remember soft costs such as customer re-approval, certification and delayed shipments, which you can add to the requalification input.

Frequently Asked Questions

What costs should be included in an engineering change?

Engineering and documentation labor, scrapped or reworked stock and WIP, tooling and fixtures, requalification and testing, and customer or certification costs. Also consider schedule delay and warranty exposure if they apply.

How do I reduce engineering change cost?

Choose use-up or serial effectivity to avoid scrapping stock, bundle related changes into one ECO, make changes early in the lifecycle, and review impact before approval. Early design reviews prevent many changes entirely.

What is a good payback period for an engineering change?

It depends on your company's hurdle rate and product life. Many organizations look for payback within 12 to 24 months for cost reduction changes, while safety or regulatory changes are driven by necessity rather than payback.

Does this include the cost of delay?

Not directly. Add any expected cost of delay, such as expediting or lost sales, to the requalification input or increase the engineering effort, so that it appears in the total one-time cost.

Netray can help pull on-hand, WIP and open order quantities straight from your ERP so each change gets an accurate write-off estimate. The calculator works on its own with your own numbers.

Talk to an Expert Explore More Free Tools

Related Tools

Engineering & PLM

More Engineering & PLM tools

See all

Back to All Tools