Accredited Calibration vs. Quality Calibration. What’s the Difference?  

Sometimes terms are used interchangeably and they shouldn’t be. Case in point: accredited calibration vs  quality calibration. Calibration terminology matters because it affects how measurement results are evaluated during an audit. This is not just wording. It determines whether your calibration records provide defensible evidence during an inspection. 

The term “quality calibration” shows up everywhere. It is on vendor websites, in promotional materials and referenced in conversation. It sounds reassuring, but “quality” is not a defined standard. Assuming all calibration is equivalent is one of the fastest ways teams end up with audit findings, corrective actions or invalid measurement data they cannot defend.  

This article explains the real difference between accredited calibration and quality calibration. We’ll explore how auditors evaluate both, and how to make a safer decision when choosing a calibration provider.   

The goal is to reduce measurement risk before it shows up in an inspection.  

Key Takeaways  

• “Quality calibration” is not a regulated or auditable standard. It is a marketing phrase that carries no formal meaning during an inspection.  

• Accredited calibration provides third-party verification of technical competence, traceability and uncertainty control.  

• Auditors evaluate calibration records as decision evidence, not as certificates of intent or vendor claims. They evaluate whether the record supports the measurement decision it was used to justify. 

• Missing uncertainty, traceability detail or measurement data increases investigation workload and audit risk.  

• Using non-accredited calibration shifts the burden of proof onto the manufacturer.  

• Accreditation reduces risk by making calibration records defensible before an audit, not after a finding. It reduces the need to repeatedly prove baseline technical competence during inspections. 

What Does “Quality Calibration” Actually Mean?  

“Quality calibration” is not a regulated term. There is no governing body that defines it, audits against it, or enforces it.  

Vendors use the phrase to describe a wide range of practices. Sometimes it means calibrated equipment or experienced technicians. Sometimes it simply means the lab believes its work is good.  

From an audit perspective, none of that is verifiable on its own.  

Auditors do not accept intent, branding language or internal claims as evidence. They look for objective proof that calibration activities meet a recognized standard. “Quality calibration” does not provide that proof.  

Key takeaway: Quality is subjective. Accreditation is verifiable.  

What Is Accredited Calibration?  

Accredited calibration means the calibration activity is performed in accordance with a formally recognized standard and is independently audited for technical competence.  

Most commonly, this means calibration performed under ISO/IEC 17025. This standard defines how calibration laboratories must demonstrate technical competence, control uncertainty, maintain traceability and operate a compliant quality management system.  

Accreditation is granted and maintained by recognized accreditation bodies such as ANAB and A2LA. These organizations audit laboratories on a recurring basis. The scope of these audits matters, as accreditation applies only to the specific measurements and ranges listed. If a measurement is not listed on the laboratory’s accredited scope, the accreditation does not apply. 

Accredited calibration is third-party verification that a lab is technically capable of performing the work it claims to perform.  

What Accreditation Bodies Actually Evaluate  

Accreditation audits are technical and go far beyond checking that a procedure exists.  

Technical Competency  

Auditors verify that the lab can actually perform the calibration being offered. This includes:  

• Equipment capability and supported measurement ranges  

• Technician training, experience, and demonstrated proficiency  

• Method validation for each measurement type  

If a lab is not accredited for a specific measurement, the accreditation does not apply.  

Measurement Uncertainty  

Uncertainty quantifies how confident you can be in the reported result.  

Accredited labs are required to calculate, control and document measurement uncertainty. This matters because decisions are made using those values. Without uncertainty, you cannot confidently decide if a result meets specifications, which increases the risk of making the wrong call.  

Traceability  

Traceability connects a measurement back through an unbroken chain of comparisons to recognized references. Traceability is not a label. It is documented evidence. This is often discussed in relation to national standards, but the critical point for auditors is evidence, not labels.  

Accredited labs must demonstrate documented traceability for each measurement performed, appropriate to the application and regulatory environment.  

Quality Management System  

Accreditation also evaluates how the lab manages its work. This includes:  

• Document control  

• Internal audits  

• Corrective action handling  

• Record retention  

• Review and approval processes  

These controls are what make calibration records defensible during inspections.  

Documentation Differences That Matter in an Audit  

Calibration certificates are often where the difference becomes visible. ISO/IEC 17025 defines specific reporting requirements that support the validity and interpretation of calibration results. Accredited calibration certificates typically include:  

• As-found and as-left measurement data  

• Defined tolerances and acceptance criteria  

• Measurement uncertainty  

• Traceability statements  

• Environmental conditions  

• Technician and quality approvals  

Non-accredited certificates often omit one or more of these elements. Pass-or-fail results without data are common. Missing uncertainty is common and missing traceability detail is common, too.  

During an audit, inspectors do not evaluate certificates in isolation. They test whether records support decisions. If the documentation cannot support what it is supposed to, it becomes a finding. This is the risk that comes with a “quality” calibration.  

Risks of Choosing a Non-Accredited Calibration Provider  

Using a non-accredited provider does not automatically mean noncompliance. It increases your responsibility to independently verify competence, uncertainty evaluation, and traceability. Common risks include:  

• Audit findings tied to insufficient documentation  

• Inability to defend prior measurement decisions  

• Increased corrective action workload  

• Recalibration and downtime costs  

• Erosion of customer and regulator confidence  

In regulated environments, avoiding unnecessary investigation work is part of risk management. Accreditation reduces the need to repeatedly prove basic competence.  

When Is Accredited Calibration Required?  

Accreditation is not universally mandated, but it is often expected.  

Accreditation is typically required for:  

• ISO-certified quality systems  

• FDA-regulated environments  

• Aerospace and defense applications  

• Medical device manufacturing  

• Customer-mandated compliance  

Accreditation may be optional for:  

• Internal reference tools  

• Non-critical measurements  

• Early R&D applications  

• Equipment not used for acceptance decisions  

The key question is not whether accreditation is technically required, but whether the organization is prepared to defend the alternative.  

Accredited vs. Quality Calibration at a Glance  

Criteria	Accredited Calibration	“Quality Calibration”
Recognized standard	Yes	No
Audit acceptance	High	Variable
Measurement uncertainty	Required	Often missing
Traceability	Documented and verified	Claimed or unclear
Certificate credibility	Defensible	Depends on vendor
Risk level	Lower	Higher

Practical Buyer Checklist  

Before selecting a calibration provider, ask:  

• Is the lab ISO/IEC 17025 accredited for this specific measurement?  

• Is the accreditation scope current and applicable?  

• Is measurement uncertainty documented?  

• Are certificates complete and audit-ready?  

• Does the provider support regulated industries like ours?  

If any of these answers are unclear, that uncertainty becomes your responsibility during an audit.  

Making the Right Calibration Choice  

Accreditation reduces the burden of proof before an auditor ever walks through the door.  

If you are evaluating calibration providers, do not rely on marketing language. Request the accreditation scope, review sample certificates and confirm uncertainty and traceability are documented.  

If you would like to review SIMCO’s ISO/IEC 17025-accredited capabilities or discuss how your current calibration program would hold up during inspection, contact our team to learn more.  

FAQ  

Is ISO 17025 calibration always required? 
No. But in regulated environments, it is often the simplest way to demonstrate technical competence and reduce audit risk.  

Can a non-accredited lab still be compliant? 
Yes, but the manufacturer must independently verify competence, methods, uncertainty, and traceability.  

Why do auditors care about uncertainty? 
Because decisions are made using measurement results. Without uncertainty, those decisions cannot be defended. Without documented uncertainty, it is difficult to confidently show that a result meets specifications. 

Does accreditation eliminate OOT events? 
No. It improves how OOTs are identified, documented, and investigated.