Total cost of quality is the full, combined cost a company incurs both to achieve the required level of quality and to deal with quality not being met. It aggregates spending on quality planning and control with the losses from defects, scrap, rework, and other failures.
Main components
Total cost of quality is commonly broken into four categories:
- Prevention costs: Activities designed to avoid defects and nonconformances, such as training, process design, mistake-proofing, quality engineering, supplier qualification, and maintenance of procedures.
- Appraisal costs: Activities to assess and verify quality, such as incoming inspection, in-process checks, testing, calibration, audits, and review of batch records or travelers.
- Internal failure costs: Costs of nonconformances detected before shipment, such as scrap, rework, retesting, yield loss, deviation investigations, engineering dispositions, and line downtime due to quality issues.
- External failure costs: Costs of nonconformances found after delivery, such as returns, field service, warranty handling, controlled rework at the customer, recalls, complaint handling, and related investigations.
In manufacturing, the total cost of quality typically includes both direct costs (labor, materials, test time) and indirect costs (capacity consumed, delays, extra planning, administrative work in quality systems).
Operational meaning in industrial and regulated environments
On the shop floor, total cost of quality connects quality metrics like defect rates, scrap percentage, and rework hours to financial and capacity impact. For example:
- In high-value or long-lead-time industries (such as aerospace or medical devices), scrap and rework can significantly affect unit margins and delivery schedules, not just quality KPIs.
- In MES, ERP, and quality systems, total cost of quality may be calculated by tagging events (scrap transactions, deviations, inspections) with cost data and aggregating them across products, lines, or programs.
- In regulated environments, the effort required for investigations, documentation, and approvals is often a substantial part of internal and external failure costs.
Total cost of quality is often used as a management metric to understand how much is being spent on prevention and appraisal compared to the cost of failures, and to evaluate the impact of quality and process improvement initiatives.
What it includes and excludes
Total cost of quality commonly includes:
- Costs tied to formal quality processes and systems (training, audits, documentation).
- Costs of direct product nonconformance (scrap, rework, concessions).
- Costs of related investigations, reviews, and approvals.
- Customer-facing failure costs such as returns and complaint handling.
It typically does not include:
- Normal production costs for conforming product.
- Strategic investments not clearly tied to quality (for example, general R&D not aimed at defect reduction).
- Broader business consequences that are hard to quantify, such as reputational impact, unless a specific method to estimate them is defined.
Relation to cost of poor quality (COPQ)
Total cost of quality is often expressed as:
Total cost of quality = Cost of good quality + Cost of poor quality (COPQ)
Here:
- Cost of good quality usually combines prevention and appraisal costs.
- Cost of poor quality (COPQ) usually combines internal and external failure costs.
In practice, many organizations focus heavily on COPQ (the failure side) because it is more visible in day-to-day operations, but the formal definition of total cost of quality always includes both prevention/appraisal and failure costs.
Common confusion
- Total cost of quality vs. COPQ: COPQ refers only to failure-related costs (internal and external). Total cost of quality also includes prevention and appraisal costs.
- Total cost of quality vs. quality budget: A quality department budget may cover a portion of prevention and appraisal activities, but many failure costs occur in production, engineering, logistics, and at customers. Total cost of quality spans all affected functions, not just the quality organization.
- Total cost of quality vs. compliance cost: Regulatory compliance activities may be part of prevention or appraisal, but total cost of quality is broader and includes nonconformance and failure-related costs.
Link to scrap and margin stability
In contexts such as aerospace manufacturing, scrap and rework are major components of internal failure cost and therefore of total cost of quality. High material value, long lead times, and constrained capacity mean that changes in scrap rates can cause large swings in unit cost, delivery performance, and program-level financial stability. When analyzed as part of total cost of quality, scrap is treated not only as a quality metric but as a key driver in economic and capacity planning.