Quality Cost

Costing Quality and Inspection: Cost per Unit, Scrap, Rework, and the Price of Poor Quality

What actually drives quality and inspection cost per unit, how to quote it defensibly, and the estimating errors that quietly erase margin.

Inspection cost per unit is labor plus equipment time plus overhead, spread across throughput. If a CMM inspector runs at a loaded rate of 55 dollars per hour and checks 12 parts per hour, direct inspection labor is about 4.58 dollars per part. Add machine amortization: a 120,000 dollar CMM over 5 years and 3,000 productive hours per year costs 8 dollars per hour, or 0.67 dollars per part. Layer in a facility and QA overhead burden, often 60 to 120 percent of direct labor. Quote the inspection step as a real line item, not a rounding buffer folded into part price.

Scrap is usually the largest hidden quality cost because it destroys full accumulated value, not just material. A part scrapped at final has absorbed raw material, every machine cycle, and every labor touch up to that point. Scrap cost per unit equals material plus value added through the scrap point, times units scrapped, divided by good units. Scrapping 30 of 1,000 parts that each carry 42 dollars of accumulated value adds 30 times 42, or 1,260 dollars, spread over 970 good units, roughly 1.30 dollars per unit. The Scrap Cost calculator anchors this to the stage where the loss actually occurs.

Rework is cheaper than scrap but still real, and estimators routinely price it at zero. Rework cost is added labor plus added machine time plus any consumables, times reworked units. If 50 units each need 8 minutes of touch-up at a 45 dollar loaded rate, that is 0.75 dollars of labor per reworked unit times 50, or 37.50 dollars, before consumables and requalification. Spread over 1,000 units it looks tiny, but at scale and low first pass yield it compounds. The Rework Cost calculator separates rework dollars from scrap so you can see which failure mode is bleeding margin.

Cost of poor quality, or COPQ, bundles the money quality problems cost across four buckets: internal failure (scrap, rework), external failure (returns, warranty), appraisal (inspection, testing), and prevention (training, tooling, error-proofing). Typical plants run COPQ at 15 to 25 percent of revenue; disciplined operations hold it near 5 to 8 percent. The Cost of Poor Quality calculator totals the buckets so you can quote quality as a managed cost, not a mystery. The key insight for pricing: shifting a dollar from failure to prevention usually returns 3 to 10 dollars downstream.

Warranty and returns belong in the quote even though they land after shipment. Reserve for them using expected return rate times cost per return. If your Warranty Return Rate runs 0.65 percent and each return costs 85 dollars in replacement, freight, and admin, that is 0.0065 times 85, or 0.55 dollars per unit shipped, that you must price in today. Underquoting this is a classic estimating error: the sale looks profitable at 8 percent margin until field failures at 1.5 percent quietly consume 1.30 dollars per unit and turn the job negative.

Build the quote as a stack, not a single number, so a customer or auditor can trace every dollar. Start with material, add direct machine time and direct labor, then add an inspection line, a scrap allowance tied to expected yield, a rework allowance, an appraisal burden, and a warranty reserve. For a part with 22 dollars material, 6 dollars labor, 4 dollars machine, 4.58 dollars inspection, 1.30 dollars scrap, 0.04 dollars rework, and 0.55 dollars warranty, cost before overhead and margin is about 38.47 dollars. Overhead at 30 percent and margin at 15 percent build from that traceable base.

Estimates go wrong in predictable places. The biggest is using yield instead of first pass yield for the scrap and rework allowance, which hides the reworked units and understates cost by the entire rework line. The second is a static scrap rate: if you quote 2 percent scrap but the process actually runs 5 percent, on 100,000 units at 42 dollars accumulated value that gap is 3,000 units times 42, or 126,000 dollars of unquoted loss. The third is ignoring inspection time on low-volume, high-mix work, where setup and first-article checks can exceed run time.

Pressure-test the quote against realistic quality levels before you send it. If the part sits at 4.0 sigma, expect roughly 6,210 defects per million opportunities and price scrap and rework for that reality, not for an aspirational 6.0 sigma. Reconcile your quoted quality cost against COPQ as a percent of the quoted price; if inspection, scrap, rework, and warranty together exceed 25 percent, either the process needs prevention investment or the price needs to rise. A defensible quote shows the customer the number and the method behind it, which wins repeat work.

Published 2026-07-01.