Rounding of Results and Measurement Uncertainties in Calibration Certificates : Guide DKD-L 13-3

Measurement results are expressed as measured quantity value and measurement uncertainty (cf. International Vocabulary of Metrology, section 2.9) and form part of every calibration. Since representation with infinite accuracy (infinite number of places) is not possible, measurement results must inevitably be rounded. At the same time, it is necessary to adjust the number of digits of the measured value of the measurement result (result value) to the measurement uncertainty to avoid suggesting an uncertainty below its actual magnitude. This guide summarises normative rules and guideline specifications offering viable strategies and examples as a recommendation for proper rounding. In this guide, the term “measurement results” refers to all measured values and their associated measurement uncertainty clearly identified as such in the report stating the results. The guide does not describe the representation and rounding of indicated values (readings of a display), nominal values or (calculated) intermediate or auxiliary values for determining the measurement result