Cost of Poor Quality

XHow to read the number

The prevention-appraisal-failure model splits quality spending into money spent stopping defects, money spent finding them, and money lost because they happened. The first two are investments you chose. The last is a bill you were sent.

The single most informative output here is not the total — it is the prevention-to-failure ratio. A plant spending far more on failure than on prevention is paying to discover its defects rather than paying to not make them, and that is a spending mix you can change without any new equipment. The classic pattern in a plant that has never measured this is appraisal-heavy and prevention-light: a lot of inspectors, very few capability studies.

The external-to-internal ratio is the second thing to look at, because it is an escape-rate signal. Failures found in-house are expensive; failures found by your customer cost several times more for the same defect, and they spend your reputation as well as your money. If external failure is a large share of the total, the containment problem is upstream of the cost problem.

Two honest cautions. First, published benchmarks put total cost of quality somewhere between 5% and 30% of revenue depending on industry and maturity, which is a range so wide it should be used to sanity-check your arithmetic and not as a target. Second, this is an estimate assembled from accounts, not a measurement. It is exactly the right tool for sizing a business case and exactly the wrong tool for claiming a saving afterwards — for that you need the measure on the process itself, before and after, which is a different job than this page does.