Does the concept of cost of non-quality mean anything to you? 😐

Every part to be remade, every product returned, every customer delay costs more than you think.

Not only do these defects erode operating margins, but they also weaken reputation, overload teams and slow down innovation.

In an industrial context where operational excellence is vital, measuring and reducing the cost of non-quality (CNQ) has become a major, and often under-exploited, lever.

This comprehensive guide helps you to:

• Understand the different components of CNQ (internal, external, hidden)

• Measure these costs in your context, even if you are starting from scratch

• Deploy effective steering indicators

• Prioritise actions according to their ROI

• Automate tracking to generate sustainable savings

• Download a ready-to-use Excel template to start your own analysis

The definition of the cost of non-quality (CNQ)

The cost of non-quality corresponds to all the losses generated by products or services that do not meet the expected requirements.

It is not just about visible defects or one-off incidents: non-quality creeps in wherever a discrepancy causes a loss.

How to calculate the cost of non-quality?

Summary formula

CNQ = Internal costs + External costs + Hidden costs − Prevention costs

Each of these components can be measured, monitored and managed.

Typology of costs to be integrated

Internal costs

• Scrap and rework

• Unused machine or operator time

• Over-testing / redundant inspections

• Storage, sorting, quarantine

External costs

• Customer returns

• Contractual penalties

• After-sales service costs (interventions, replacements)

• Loss of turnover on the concerned sale

Hidden costs

• Damage to brand image

• Turnover related to stress or loss of purpose

• Administrative time dedicated to complaints

• Loss of interest from certain customers or partners

• Impact on OEE, lead times or innovation

Prevention costs

• Quality controls

• Preventive maintenance

• Internal audits

• Training

💡 The cost of non-quality is a cross-functional indicator of the organisation's performance.

Why integrate prevention in the calculation

Too often, CNQ is calculated without taking into account the efforts already made to avoid defects.

However, these expenses (training, audits, maintenance, controls, etc.) help to limit invisible losses.

A good quality indicator must contrast what you invest with what you lose.

Step-by-step method: how to measure CNQ in your business

Step 1: Define the scope

Start small: one line, one workshop, one product. It is faster and more credible.

Step 2: Identify cost items

You can start with a simple spreadsheet (like the one proposed below):

• Internal costs: scrap, rework, reprocessing

• External costs: penalties, after-sales service, returns

• Hidden costs: conservative estimates

• Prevention costs: training, audits, maintenance

Step 3: Collect data

Use your existing systems (ERP, MES, CRM, Excel files). Even if they are incomplete, you can start with orders of magnitude.

Step 4: Calculate the CNQ % of turnover

Example: If CNQ = £120,000 and turnover = £3M → CNQ/Turnover = 4%

This allows for benchmarking and setting improvement targets.

Worked example

Let's take the example of a mechanical subcontracting company.

Here are its figures:

Monthly production: 20,000 parts
Defect rate: 2.5%
Unit cost: £40
Average rework cost: £12
Estimated external costs: £6,000
Estimated hidden costs: £4,000
Prevention costs: £8,000

Calculation:

• Scrap: 250 × £40 = £10,000

• Rework: 250 × £12 = £3,000

• Gross total: 10,000 + 3,000 + 6,000 + 4,000 = £23,000

• Net CNQ = 23,000 − 8,000 = £15,000 / month

This equates to £180,000 / year, without taking into account image or delay impacts.

KPIs to track to manage the cost of non-quality

A good dashboard allows you to identify trends, recurrences and high-impact causes.

Integrating a preventive approach: the real performance lever

Measuring is good. But anticipating is better 😊

Today, the most successful companies use their quality data to prevent defects, not just to record them.

A few examples:

• An analysis of non-conformities makes it possible to detect invisible root causes (e.g. raw material variation)

• Real-time alerts on certain drifts (cycle time, temperature, vibration, etc.) prevent scrap before it happens

• A well-structured CAPA database allows problems to be resolved from the 1st occurrence, not the 10th

📈 Reducing the cost of non-quality is about anticipation, not just reaction.

Moving from a catch-up culture to a control culture

The cost of non-quality is an excellent indicator of industrial maturity.

Knowing how to measure, manage and reduce it, with methodology, allows you to:

✅ Increase margins
✅ Smooth out production
✅ Restore customer trust
✅ Strengthen team commitment

Excel template to download

We offer you an Excel template to:

• Simulate your own cost of non-quality

• Estimate the gains associated with a corrective action

• Track monthly trends