Laboratories and companies using measuring instruments or measurement standards in their processes need to know the uncertainty of these measurements.

This knowledge is achieved by calibrating measuring instruments. A task which is mainly carried out by accredited calibration laboratories.

When performing calibration, a calibration laboratory defines the relationsship between a measuring instrument or the printed value of a measurement standard and the value of a reference standard. This reference value is established by the calibration laboratory and is traceable to the SI-unit system.

The result of a calibration can be expressed in terms of information about the views, the instrument provides for the respective reference values.

In many cases the measurement uncertainty of the measuring instrument will also be shown, which is given by the difference between the display of the measuring instrument or a measurement standards printed value and the reference value.


Calibration is often confused with adjustment, where the measurement uncertaincy is usually set to be zero.

If a measuring instrument or a measurement standard is adjusted, it must be agreed with the customer, and the calibration laboratory must calibrate the measuring instrument or the measurement standard both before and after adjustment. For users of measuring instruments and measurement standard the history of the calibration results is critical in order to define the time interval between calibrations and to be able to assess the values measured with the measuring instrument or the measurement standard in day-to-day work.


  • Acceleration and speed
  • Acoustics and ultrasound
  • Chemical
  • Density and viscosity
  • Geometry
  • Elektricity DC and LF
  • Elektricity HF
  • Flow
  • Force and torque
  • Hardness
  • Moist
  • Ionizing radiation
  • Magnetism
  • Mass
  • Optics
  • Pressure and vacuum
  • Reference material
  • Temperature
  • Time and frequency
  • Volume


Below are links or references to documents for the specific scheme.



  • DS/EN ISO/IEC 17025, 2017 General requirements for the competence of testing and calibration laboratories.



In addition to the above requirements documents, that the calibration laboratory must comply with, there are a number of international guidelines that are relevant to the accredited laboratories and implemented through the accreditation regulations.:

  • EA-4/02:2013: Evaluation of the Uncertainty of Measurement in Calibration
  • EA-4/14:2003: The Selection and Use of Reference Materials
  • EA-4/18:2021: Guidance on the level and frequency of proficiency testing participation
  • ILAC G8:09/2019: Guidelines on Decision Rules and Statements of Conformity
  • ILAC G19:06/2022 Modules in a Forensic Science Process
  • ILAC G24:2022: Guidelines for the determination of recalibration intervals of measuring equipment



Various accreditation messages(in Danish only) have been published to guide and describe evaluation practice and issues relevant for accredited calibration laboratories.