UKAS Calibration
ISO17025 and ISO9001 Quality Management Systems

What is UKAS Calibration?

Calibration, basically involves the comparison of a measuring instrument, the Unit Under Test (UUT) to a Standard of known accuracy. The standard would ideally be more accurate than the UUT and have its own calibration certificate which can be traced back through an unbroken chain of calibrated standards to an appropriate standard held by a National Laboratory. In the UK, this would be the National Physical Laboratory (NPL).

UKAS Calibration is essentially calibration undertaken by a laboratory which has been independently audited and subsequently accredited by UKAS to carry out the work.

What is UKAS?

UKAS (United Kingdom Accreditation Service) is the sole body recognised by HM Government for assessing and accrediting the competence of calibration and testing laboratories.

UKAS Accreditation, ISO 17025 and ISO 9001

Laboratories are accredited by UKAS to ISO 17025 which is the internationally recognised standard for the competence of calibration and testing laboratories.

Our own systems, people, their training, and our technical capabilities are regularly and thoroughly examined and tested by a team of UKAS auditors, each of them specialists in their field. It is an expensive and time consuming process, but our ongoing accreditation and fulfilment of the requirements of ISO 17025 means you can rest assured that we have the competence, impartiality and performance capability necessary to consistently deliver technically valid calibration results each and every time.

Accreditation to ISO17025 also means our quality management systems meet the principles of ISO 9001. This is endorsed by three major international organisations' the International Organisation for Standardisation (ISO), the International Laboratory Accreditation Co-operation (ILAC), and the International Accreditation Forum (IAF).

Separate certification of an accredited laboratory to ISO9001 is therefore unnecessary for calibration activities.

Certification of a laboratory to ISO 9001 alone, relates only to the laboratory's quality management systems, not the technical competence of the laboratory. A laboratory that is certified to ISO 9001 only, and is not accredited to ISO 17025 should not be considered an acceptable alternative to a UKAS laboratory.

Our UKAS Certificate of Accreditation can be downloaded from our 'Downloads' page.

It is important to note however that UKAS accreditation of a calibration laboratory does not necessarily mean that the laboratory can issue UKAS certificates for everything that it calibrates. Each individual calibration technique has to be separately accredited. The laboratory's 'UKAS Schedule of Accreditation' will detail the activities for which they have been accredited.

Our UKAS Schedule of Accreditation can be downloaded from our 'Downloads' page.

If you are unsure whether we or any other laboratory is UKAS accredited to carry out a particular calibration for you, you can check the Schedule of Accreditation. Or better still, just ask, because sometimes the publishing of the latest Schedule can lag a little behind the latest accreditations attributable to a laboratory.

UKAS Calibration Certificates

A UKAS Calibration Certificate will be ISO17025 compliant and should be instantly recognisable by the UKAS Accreditation Symbol depicting the Royal Crown which is printed in the top right hand corner of the front page. An example is shown at the foot of this page.

The certificate should detail the measured results of the calibration, both before and after any adjustments if this is appropriate. It should also detail the uncertainty that is associated with the reported results.

It is not however, possible to obtain a UKAS calibration certificate for every conceivable piece of measuring equipment. There are instances where for some types of instrument, no laboratory has been accredited. Or maybe a UKAS laboratory has additional capabilities which have not been formally accredited. A 'Traceceable' or 'In-House' or "Class 1" (they're all the same thing) calibration certificate would usually be offered in these circumstances. Whilst not bearing the UKAS symbol with Royal Crown, this certificate should at the very least detail the measured results of the calibration and the associated uncertainty of measurement. It should also list any standards used to perform the calibration, thereby providing documented traceability to National Standards.

Unfortunately many manufacturers 'calibration certificates' supplied with new instruments do not meet any of the above requirements. This makes them no more than 'Certificates of Conformity' rather than true calibration certificates. These would not normally be acceptable to an auditor.


A UKAS calibration
certificate should
display this symbol.